Integration of recognition elements with macromolecular scaffolds: Effects on polymer self-assembly in the solid state

Article abstract of DOI:10.1021/ma0495590

Polystyrene scaffolds were grafted with model functionalities featuring strongly interacting hydrogen bonding and aromatic stacking elements. Both glass transition temperatures and degree of microphase separation in functionalized block copolymers depend

Full text of DOI:10.1021/ma0495590

Macromolecules 2004, 37, 4931-4939
4931
Integration of Recognition Elements with Macromolecular Scaffolds:
Effects on Polymer Self-Assembly in the Solid State
Roy Sh en h a r , Am ita v Sa n ya l, Ok ta y Uzu n , Hir osh i Na k a d e, a n d
Vin cen t M. Rotello*
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
Received March 4, 2004; Revised Manuscript Received April 16, 2004
ABSTRACT: Polystyrene scaffolds were grafted with model functionalities featuring strongly interacting
hydrogen bonding and aromatic stacking elements. Both glass transition temperatures and degree of
microphase separation in functionalized block copolymers depend on the nature of the functionality and
in particular on the strength of intermolecular interactions. The polymers under study were amorphous;
it was found, however, that domain periodicities of functionalized diblock copolymers in the microphase-
separated state are extremely sensitive to local interactions between functionalities and can express even
subtle differences in interaction strength. The results emphasize the ability to fine-tune polymer
microstructure and thermomechanical behavior using supramolecular chemistry.
In tr od u ction
In this paper we analyze the effects of recognition
units (i.e., units that interact through noncovalent
interactions) on solid-state properties of random and
block copolymers through a comparison between four
different model functionalities: diamidopyridine (DAP),
which is capable of molecular recognition through
multiple hydrogen bonding interactions, anthracene
carboxylate (Anth) and pyrene carboxylate (Pyr), which
are capable of aromatic stacking interactions of varying
affinity,13 and diesterpyridine (DEP), offering the weak-
est intermolecular interaction. In our study, we probed
the influence of parameters such as interaction strength
and structural rigidity on glass transition temperatures
and microphase separation in block copolymers. Our
results demonstrate that noncovalent interaction capa-
bilities of side-chain groups impact the physical behavior
of polymers in a predictable fashion, providing a ver-
satile and tunable tool for manipulation of polymer
properties.
The ability to synthesize polymers in a controlled or
living fashion1 facilitates the ability to manipulate
polymer microstructure, providing a versatile tool for
nanotechnology. One prominent example is the phe-
nomenon of microphase separation exhibited by block
copolymers, which can be harnessed to create well-
defined periodic microdomains of controlled morpholo-
gies (e.g., cylinders, spheres, lamellae) on the 10-100
nm scale, a key size scale for emerging technologies.2
Apart from relative block volumes, a key parameter that
can be used to control the size and morphology of the
microdomains is the effective incompatibility between
the different blocks,3 which is determined by the essence
of comonomers involved.
As the research concerning the solid-state structure
of block copolymers deals mainly with polymers that
consist of common monomers (e.g., isoprene, styrene,
acrylates, and epoxides), the ability to tune the incom-
patibility as desired is very limited. Polymer function-
alization, apart from extending the horizon of polymer
properties in general, can offer another handle to control
phase architecture by fine-tuning both volume fractions4
and incompatibility.
Recent studies have demonstrated the ability to use
supramolecular chemistry5 as a novel method for poly-
mer synthesis6 including creation of special polymeric
structures such as block, star, and graft polymers.7,8
Supramolecular chemistry also affords unique ways for
polymer functionalization9 and facilitates formation of
nanoobjects.4 Polymers modified with recognition units
can be used to assemble nanoparticles into discrete
structures10 and for creation of molecularly imprinted
sensor matrices.11 Undoubtedly, the utilization of non-
covalent interactions opens new avenues in applied
polymer research; nevertheless, while the main atten-
tion is being drawn to the constructing abilities of
noncovalent interactions, the underlying direct influence
of these interactions on the solid-state structure and
behavior of amorphous polymers has been little studied
to date.12
Resu lts a n d Discu ssion
Con str u ction of F u n ction a liza ble P olym er Sca f-
fold s. Versatile polystyrene scaffolds consisting of
styrene and 4-chloromethylstyrene (CMS) comonomers
were used for these studies. With these polymers, the
chloromethyl groups provide “hooks” for postpolymer-
ization attachment of different functionalities through
nucleophilic substitution (Scheme 1). This approach
offers two main advantages for investigation of struc-
ture-property relationship relative to copolymers com-
posed of very different or prefunctionalized comono-
mers: (a) using styrene derivatives (i.e., CMS) as the
functionalizable monomers in the polystyrene scaffolds
enables use of the functionalities as side-chain modifiers
to an all-polystyrene backbone, isolating the contribu-
tion of the attached functionality to the material prop-
erties of the polymer14 and allowing comparison to the
known properties of polystyrene, and (b) it allows true
comparison between functionalities while maintaining
all parameters pertaining to the polymer (particularly
the degree of randomness in the random copolymer/
blocks) constant, since the functionalities are grafted
to the exact same polymer scaffold.
* To whom correspondence should be addressed: Tel (413) 545
2058; Fax (413) 545 4490; e-mail rotello@chem.umass.edu.
10.1021/ma0495590 CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/05/2004

4932 Shenhar et al.
Macromolecules, Vol. 37, No. 13, 2004
Ta ble 1. Molecu la r Attr ibu tes of P a r en t P (S-co-CMS) a n d P S-b-P (S-co-CMS) P olym er Sca ffold s
Mn (kg/mol)a
P(S-co-CMS)
functionality content
(mol %)a,d,e
notation
series
PSb
total
PDIa
DPa,c,d
PS/CMS (25, 50%)
24.8
12.8
12.7
13.2
20.1
23.1
26.2
24.8
40.1
39.8
41.0
47.2
50.2
53.3
1.46
1.26
1.16
1.25
1.23
1.23
1.25
194
377
370
374
434
464
489
50
17
25
40
25
20
22
PS/CMS (27:13, 17%)
PS/CMS (27:13, 25%)
PS/CMS (28:13, 40%)
PS/CMS (27:20, 25%)
PS/CMS (27:23, 20%)
PS/CMS (27:26, 22%)
A
A, B
A
B
B
27.3
27.1
27.8
27.1
27.1
27.1
B
a
b
d
According to SEC with PS standards. PDI of all PS blocks were ca. 1.1. c Average total degree of polymerization. Calculated from
1H NMR integration. e Molar percentage of CMS (in the case of block copolymers represents the percentage within the functionalized
block only).
Sch em e 1. Sch em a tic Illu str a tion of
P ostp olym er iza tion F u n ction a liza tion of a
P olystyr en e Ba ck bon e th r ou gh Nu cleop h ilic
Su bstitu tion of Ch lor id e Gr ou p s
The polymer scaffolds were synthesized through
controlled free-radical polymerization using nitroxide
initiators,15 affording relatively narrow polydispersities
F igu r e 1. General structure of monoblock and diblock co-
as well as the ability to create block-random copoly-
mers (which we denote simply as “block copolymers” for
brevity). Characteristics of the polymer scaffolds used
in this study are summarized in Table 1, and their
general structure is depicted in Figure 1 (where R )
Cl). The attributes of the scaffolds (i.e., number-aver-
aged molecular weights (Mn) and functionality molar
fractions) were also used for the general polymers’
notation: PS/X(Mn,z) and PS/X(MPS:Mfunc-PS,z) denote
polystyrene-based random and diblock copolymers, re-
spectively, which are modified to a molar percentage z
with the functionality X.16 We note that for consistency
usage of the term “functionality content” (and analogous
terms) when regarding diblock copolymers always refers
to the functionality content in the functionalized block
only.
The diblock copolymers used in this study form two
fundamental series, which we denote A and B (see Table
1), and are meant to probe different characteristics of
the microphase separation phenomenon. Series A is
comprised of three polymers with compositional char-
acteristics of (27:13,17%), (27:13,25%), and (28:13,40%),
in which the molecular weights in both blocks remains
constant ((1 kDa) while the functionality content is
varied. This series thus allows the investigation of the
influence of the functionality content parameter on the
effective incompatibility that leads to microphase sepa-
ration. Series B, on the other hand, consists of four
polymers having compositional characteristics of (27:
13,25%), (27:20,25%), (27:23,20%), and (27:26,22%),
which are all made from the same batch of the first block
(PS) and in which the functionality content is very
polymers and model functionalities used in this study. R ) Cl
corresponds to the parent polymer scaffolds.
similar. This series therefore allows quantitative prob-
ing of the contribution of varying polymer lengths
(derived from changes in the functionalized block lengths)
to the bulk periodicity of the microphase-separated
melts at similar functionality content (vide infra).
Mod el F u n ction a lities. There are two major factors
that affect the solid-state behavior of amorphous poly-
mers: the strength of interaction between polymer
segments and structural attributes of the components
such as steric bulk and rigidity. The model functional-
ities used in this study (Figure 1) feature different
modes of noncovalent interaction with different degrees
of strength while maintaining similar molar volumes
(within (4% of the modified monomer).
As probes for aromatic stacking, we studied 9-an-
thracene carboxylate (Anth)17 and 1-pyrene carboxylate
(Pyr) (Figure 1). In solution, aromatic stacking of
anthracene units was demonstrated to induce a folded
chain structure in anthracene-functionalized poly-
styrenes and enabled hosting electron-poor molecules
such as picric acid.18 Pyrene offers a stronger π-stacking
interaction than Anth.13 Moreover, the excimer emission
of pyrene facilitates spectroscopic characterization of the
aromatic stacking interaction; ground-state aggregation
of pyrene groups in pyrene-functionalized polymers in
solution has also been reported.19,20 Figure 2 shows the
fluorescence spectra of solutions and thin films of Pyr-
functionalized polystyrenes. All emission spectra are

Macromolecules, Vol. 37, No. 13, 2004
Macromolecular Scaffolds 4933
Figu r e 3. Preferred dimerization arrangement of DAP through
two-point hydrogen bonding.23
F igu r e 2. Fluorescence spectra of PS/Pyr (25, 50%) in
chloroform solution (a) and as thin film (b) and of thin films
of PS/Pyr diblocks of series A with decreasing Pyr content: (c)
(28:13, 40%), (d) (27:13, 25%), and (e) (27:13, 17%). The
characteristic emission bands of free pyrene and of the excimer
have been denoted. Spectra are normalized to the intensity of
the excimer peak and are vertically offset for clarity.
F igu r e 4. Infrared spectra showing N-H and C-H stretching
modes: (a) Bz-DAP in chloroform solution and (b) in the solid
state, (c) solid PS/DAP(28:13, 40%). The free N-H stretch and
the hydrogen-bonded N-H stretching region have been de-
noted. Spectra are offset for clarity.
dominated by the excimer emission band (at ca. 500-
510 nm), which is attributed to formation of ground-
state aggregates of the Pyr functionality.19 Comparison
between emission patterns of PS/Pyr(25,50%) in solution
and in the solid state (Figure 2a,b) reveals both a blue
shift of the excimer emission and disappearance of the
emission peaks of free pyrene (at 392 and 412 nm). This
indicates, on one hand, enhanced formation of Pyr
aggregates and, on the other hand, that the excimer
components are improperly oriented in the glassy
polymer matrix they are attached to.21
The fluorescence from films of the diblock copolymers
of PS/Pyr of series A (Figure 2c-e) reveals that decreas-
ing Pyr content results in a further blue shift of the
excimer peak and an increase in the relative intensity
of the free pyrene emission. This corroborates the
previous result, as it is to be expected that in glassy
polymer matrices with smaller density of functionality
the statistical chance to form dimers decreases (hence
the intensification in the free pyrene emission bands)
and that the dimers formed would be more spatially
constrained and therefore improperly oriented than in
polymers with higher functionality content (hence the
blue shift in the excimer emission).21
both Bz-DAP and PS/DAP(28:13,40%) (a representative
DAP-functionalized polymer) exhibit multiple, broad,
and red-shifted N-H stretching modes at 3290-3300
cm-1 (Figure 4), which are attributed to hydrogen-
bonded N-H groups.11b One of our goals was to probe
the influence of this dimerization interaction on the
polymer structure and thermal behavior12 and to gain
insight into the role of hydrogen bonding in these
systems by comparison to other model functionalities.
The analogous 2,6-diesterpyridine (DEP) was used as
control for DAP (Figure 1). DEP is highly analogous in
structure to DAP but can only interact with other DEP
functionalities through dipolar interactions, making it
closer in interaction strength to Anth and Pyr. It should
be noted, that despite the similarity in volumes between
all four functionalities, DEP and DAP are much more
flexible entities than the polycyclic Anth and Pyr. This,
therefore, makes DEP a useful “yardstick” by which
each observed effect could be attributed either to the
strength of interaction or to structural rigidity based
on comparison to DAP, Anth, and Pyr.
Gla ss Tr a n sition Tem p er a tu r e. Among the most
important, complex, and unsolved physical problems in
material science is the glass transition phenomenon,
which is the thermal transition in polymers from the
hard glassy state to the soft rubbery state.25 Technologi-
cally, the glass transition is of crucial importance, as it
dictates thermomechanical behavior and hence process-
ing conditions (e.g., molding temperatures). In block
copolymers, overcoming the glass transition tempera-
ture (either by thermal annealing or by solvent plasti-
cization) is required in order to enable relaxation into
the thermodynamically stable, microphase-separated
structure and to eliminate structural defects.
Hydrogen bonding was explored using 2,6-diacyldi-
amidopyridine (DAP) (Figure 1), which is of general
interest due to its ability to form host-guest recognition
dyads through three-point hydrogen bonding with
complementary groups such as uracils.9,22 In terms of
self-interaction, the hydrogen donor-acceptor-donor
arrangement existing in DAP enables DAP-DAP dimer-
ization through two-point hydrogen bonding (Figure
3).23 While in solution such dimerization is weak [Kdim
∼ 10-1 M-1 in chloroform as known from NMR titration
studies24 and also as evidenced by the single, sharp
N-H stretching mode at 3424 cm-1 exhibited by the
analogous
4-benzyloxy-3,5-dipropamidopyridine
In the simplified description of the phenomenon, the
glass transition occurs when a certain “free volume” is
reached that allows freedom of motion for the chain
(Bz-DAP), Figure 4], hydrogen bonding is prominent in
the solid state. The infrared spectra of solid samples of

4934 Shenhar et al.
Macromolecules, Vol. 37, No. 13, 2004
other hand, is expected to impart additional chain
stiffness, which also contributes to an increased Tg.
In block copolymers that have the composition (28:
13,40%), where the functionalized blocks feature func-
tionality content that is only slightly lower than that of
the previously described random copolymers (25,50%),
the increased Tg’s of the functionalized blocks imparted
by the Pyr, Anth, and DAP functionalities result in two
distinct transitions (Figure 5b). This situation clearly
indicates microphase separation in those polymers,
where the PS domains soften at 106-107 °C and Anth-,
Pyr-, and DAP-functionalized-PS domains become rub-
bery at 125, 126, and 139 °C, respectively.30 This does
not imply that the diblock copolymers of PS/DEP or even
PS/CMS do not microphase separate upon annealing (as
will be seen later, PS/DEP(28:13,40%) does create a
microphase-separated structure); it demonstrates, how-
ever, that distinction in the thermomechanical behavior
between the PS and the functionalized-PS domains
cannot be achieved using DEP, while it can be readily
obtained using functionalities that are capable of non-
covalent interactions. The distinction between the ther-
momechanical properties of PS and functionalized-PS
domains in PS/Anth, PS/Pyr, and PS/DAP makes these
materials thermoplastic elastomers;12 i.e., materials that
can be repeatedly softened under the application of heat
(thermoplastic behavior) and upon cooling to tempera-
tures between the Tg’s of the PS and functionalized-PS
domains retain elastic properties similar to cross-linked
elastomers due to the “physical cross-linking” of the
rubbery (PS) domains by the glassy (functionalized-PS)
domains.
Micr op h a se Sep a r a t ion in Block Cop olym er s.
The physical origin of microphase separation in block
copolymers is the incompatibility between different
polymer segments.31 The covalent bond connecting
between the polymer blocks prevents phase separation
on a macroscopic length scale; coupling this property
with the tendency to reduce interfacial area between
the distinct polymer domains (phases) gives rise to
periodic microdomains with tuned morphology (e.g.,
lamellae, cylinders, spheres), which is controlled through
both the block volume fractions and the degree of
incompatibility.3
The incompatibility between blocks A and B in a
diblock copolymer PA-b-PB is quantified by the Flory-
Huggins interaction parameter øAB, which is a dimen-
sionless parameter that can be expressed in terms of
attractive energy elements as follows:32
F igu r e 5. DSC scans of PS/CMS, PS/DEP, PS/Pyr, PS/Anth,
and PS/DAP: (a) (25, 50%) random copolymers and (b) (28:
13, 40%) diblock copolymers.
segments and thus enables execution of cooperative
motions. There are two main factors that dominate the
glass transition phenomenon: cohesive forces and chain
stiffness.26 With regard to the polymers discussed in this
paper, noncovalent interactions give rise to increased
cohesion between chains.8,27 Additionally, bulky and
rigid side-chain groups, which substantially increase the
barrier for rotation, increase chain stiffness and hence
are expected to increase the glass transition tempera-
ture (Tg).28
Figure 5a shows differential scanning calorimetry
(DSC) scans obtained for the random copolymer scaffold
PS/CMS(25,50%) and the corresponding functionalized
polymers PS/DEP, PS/Anth, PS/Pyr, and PS/DAP, for
which glass transition temperatures of 107, 102, 131,
128, and 149 °C, respectively, are measured. While the
PS/CMS scaffold and the polymer modified with the
DEP functionality show Tg’s that are similar to that of
PS (100 °C),29 those corresponding to PS/Pyr, PS/Anth,
and PS/DAP are substantially higher.
The weak effect on glass transition temperature
induced by functionalization with DEP indicates both
weak interaction between DEP units and a small
contribution to the overall chain stiffness, with an
additional plasticization effect induced by the flexible
alkyl substituents. As DAP is structurally very similar
to DEP, the largest effect observed with PS/DAP must
therefore be associated mainly with its ability to interact
through hydrogen bonding, which enhances overall
cohesion between the chains. In contrast, the increased
Tg’s observed for PS/Pyr and PS/Anth probably arise
from both cohesive forces and chain stiffness. Increased
cohesion in PS/Anth and PS/Pyr arises from aromatic
stacking between the functionalities (accounted for by
the fluorescence spectra of PS/Pyr films shown above)
and possibly also from stacking interactions between the
functionality and phenyl rings in the PS chains. The
structural rigidity of the Anth and Pyr units, on the
øAB (ꢀAA + ꢀBB - 2ꢀAB)/2kT
(1)
where ꢀAA and ꢀBB describe the attraction between
polymer segments of the same type (that favor phase
separation), ꢀAB represents the attraction between the
two types of segments (and is thus related to the
enthalpic gain from mixing), and k and T are the
Boltzmann constant and the absolute temperature,
respectively. In block copolymer systems that exhibit
phase separation (i.e., where no strong attraction exists
between the two blocks to overwhelm the mixing prefer-
ence of like segments), the value of ø is positive. In the
context of this paper, functionalizing block B, for
instance, with units that interact with each other will
mainly affect the term ꢀBB by increasing its value, which
in turn results in an overall increase of the incompat-
ibility between the blocks.

Macromolecules, Vol. 37, No. 13, 2004
Macromolecular Scaffolds 4935
Ta ble 2. Dom a in P er iod icities a n d Molecu la r Attr ibu tes of th e F u n ction a lized Diblock Cop olym er s
composition
(27:13, 17%)
series
A
Na,b
xb,c
f b,d
a (Å)
D (nm)e
morphologyf
DEP
Anth
Pyr
DAP
DEP
Anth
Pyr
DAP
DEP
Anth
Pyr
DAP
DEP
Anth
Pyr
DAP
DEP
Anth
Pyr
DAP
DEP
Anth
Pyr
416
412
415
417
426
420
425
428
463
453
460
466
523
514
520
526
548
539
545
551
594
582
590
597
0.38
0.36
0.37
0.39
0.50
0.49
0.50
0.51
0.67
0.65
0.67
0.68
0.50
0.49
0.50
0.51
0.43
0.42
0.43
0.44
0.47
0.45
0.46
0.47
0.37
0.36
0.37
0.37
0.39
0.38
0.39
0.39
0.42
0.41
0.42
0.43
0.50
0.49
0.50
0.50
0.52
0.52
0.52
0.53
0.56
0.55
0.56
0.56
6.8
6.8
6.8
6.8
6.8
6.8
6.9
6.8
6.8
6.9
6.9
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
6.8
23.2
23.6
27.5
23.0
22.8
23.9
26.9
27.9
28.7
30.2
34.8
26.5
25.4
27.4
31.4
26.6
26.1
28.0
32.5
27.8
27.2
29.2
33.7
(27:13, 25%)
(28:13, 40%)
(27:20, 25%)
(27:23, 20%)
(27:26, 22%)
A,B
A
lamellar
lamellar
lamellar
lamellar
B
lamellar
lamellar
B
lamellar
lamellar
B
lamellar
lamellar
DAP
a
b
Volume-effective degree of polymerization (using PS repeat unit as the reference volume). Calculated from Mn values of corresponding
PS/CMS scaffolds, functionality content, and the respective calculated molar volumes of styrene and functionalized styrene (see
Experimental Section). c Volume fraction of the functionality in the functionalized block (i.e., volume-corrected functionality content).
d
Volume fraction of the functionalized blocks. e Calculated from Lorentz-corrected intensity (q2I vs q) plots (assuming lamellar morphology
based on volume fractions). f Determined from relative location of secondary maxima in the SAXS curves with respect to the first Bragg
reflection.
As the diblock copolymers under investigation are not
pure block copolymers but rather block-random copoly-
mers, the effective incompatibility (øeff) varies with the
volume fraction of the functionality in the functionalized
block (x) as follows:33
obtained by extrapolation of the strong segregation
theory (eq 4) to the weak segregation limit (WSL).36
While the results differ by about 20% when øeffN ) 10,
this different rapidly decreases at higher segregation
strengths (e.g., 5% at øeffN ) 40). Therefore, for practical
purposes, the use of eq 4 can be extended within
reasonable accuracy into the intermediate segregation
regime.42 For block copolymers that feature weaker
segregation, a refinement that employs eq 3 with an
intermediate exponent value (0.17 < p < 0.50) should
give a reasonable and internally consistent estimate of
øeff.
Equations 1-4 set the theoretical framework for an
investigation of the effect of noncovalent interactions
on microphase-separated structures in the functional-
ized block copolymers under study.12c The molecular
characteristics and the calculated domain periodicities
of the functionalized diblock copolymers are summarized
in Table 2.
øeff ) x2øS,S-X
(2)
where S-X denotes styrene modified with the function-
ality X. The effective incompatibility can be estimated
from the domain periodicity (D) of the microphase-
separated bulk, calculated from the first Bragg reflec-
tion in the small-angle X-ray scattering (SAXS) curve.
According to Vavasour and Whitmore, the periodicity
scales with the effective incompatibility and the effective
degree of polymerization (N) as follows:34
p+1/2
D
aøeff pN
(3)
where a is the average statistical segment length
(calculated with respect to a reference monomer vol-
ume). The scaling power p changes with the degree of
microphase separation (quantified by the product øeffN).
While in the disordered state p ) 0 (the characteristic
length scale is 1.318aN1/2, reflecting Gaussian chain
statistics),35 immediately after crossing the critical point
the exponent jumps to ∼0.5,36,37 and as the degree of
microphase separation increases, it gradually decreases
and levels off at the strong segregation limit (SSL, øeffN
> 100) at p ) 1/6.38 The exact expression for the lamellar
structure in the SSL originally derived by Semenov,39
which is in agreement with other segregation theories40
and with experiment,41 is given in eq 4.
Figure 6 shows the SAXS curves of polymers of series
A functionalized with either one of the four functional-
ities. Throughout this series, the respective volumes of
the PS block and of the functionalized-PS block as well
as the effective degrees of polymerization are very
similar while the functionality content is varied between
17% and 40%. At the lowest functionality content (17%),
the SAXS profiles of PS/DEP, PS/Anth, and PS/Pyr
exhibit either a broad scattering peak (PS/DEP and PS/
Pyr) or no reflections at all (PS/Anth), evidencing very
low incompatibility between the functionalized block
and the PS block in these polymers.43 PS/DAP, in
contrast, is clearly microphase-separated, indicating a
larger value of øS,S-DAP. As the functionality molar
fraction is raised to 25% and 40%, all polymer samples
exhibit scattering peaks that are shifted toward low
angles (corresponding to larger periodicities) in ac-
cordance with increased incompatibility (eqs 2 and 3).
Dimerization of the DAP units through the relatively
D ) 1.10aøeff1/6N2/3
(4)
Matsen and Bates compared the prediction of D from
self-consistent mean-field theory with values that are

4936 Shenhar et al.
Macromolecules, Vol. 37, No. 13, 2004
F igu r e 7. SAXS profiles of polymers of series B functionalized
with DEP, Anth, Pyr, and DAP functionalities: (a) (27:20,
25%), (b) (27:23, 20%), (c) (27:26, 22%). Curves are offset for
clarity.
F igu r e 6. SAXS profiles of polymers of series A functionalized
with DEP, Anth, Pyr, and DAP functionalities: (a) (27:13,
17%), (b) (27:13, 25%), (c) (28:13, 40%). Curves are offset for
clarity.
alized with these units show very similar periodicities
in the microphase-separated samples, indicating similar
incompatibility values (i.e., øS,S-Anth = øS,S-DEP). Func-
tionalization with Pyr, featuring enhanced aromatic
stacking capability (compared to that of Anth),13 leads
to an even higher incompatibility, and as mentioned
above, the much stronger hydrogen-bonding interactions
in PS/DAP polymers lead to a significant enhancement
in the degree of microphase separation.
To obtain a quantitative evaluation of the incompat-
ibility for each of the functionalities, we employed the
polymers of series B. The polymers in this series are
highly analogous44 and feature a relatively low and
fairly uniform functionality content; this is crucial for
the reference to the functionalized blocks as random
copolymers and allows, to a reasonable approximation,
modeling the scaling of the periodicity with N according
to the same power law (eq 3) for each of the function-
alities.45
Figure 7 shows the SAXS profiles of the three longest
polymers of series B, where the qualitative order of
øS,S-DEP = øS,S-Anth < øS,S-Pyr , øS,S-DAP can clearly be
estimated from the positions of the first Bragg reflec-
tions and the existence of higher order reflections. As
PS/DAP polymers feature the highest degree of segrega-
tion, eq 4 should be more accurately applicable to them
than to polymers functionalized with the other func-
tionalities. The average value of øS,S-DAP calculated
strong multiple hydrogen-bonding interactions results
in the largest incompatibility between the functionalized
block and the PS block in PS/DAP polymers, as mani-
fested by the largest periodicities measured among the
four functionalities as well as an appearance of higher
order reflections already at low functionality content
(e.g., 25%). Appearance of higher order reflections
indicates enhanced ordering of the domains and the
scattering pattern (i.e., location of the secondary maxima
in relation to that of the first Bragg reflection q*)
enables determination of the morphology. In qualitative
agreement with our estimation of volume fractions, PS/
DAP(27:13,25%) (ffunc-PS ) 0.39) exhibits thickness-
asymmetric lamellae, while the functionalized polymers
of the (28:13,40%) composition (ffunc-PS ) 0.41-0.43),
which exhibit volume fractions of the functionalized
block that are closer to f ) 0.5, reveal close-to-symmetric
lamellar morphology (as indicated by the attenuation
of the second-order peak at 2q*).
Each quartet of functionalized polymers that originate
from the same scaffold features almost identical molec-
ular parameters (i.e., volume fractions and effective
degrees of polymerization). As such, the periodicity
serves as a measure for the degree of interaction
afforded by the corresponding functionality. It is im-
portant to note that despite the fundamental structural
difference between DEP and Anth, polymers function-

Macromolecules, Vol. 37, No. 13, 2004
Macromolecular Scaffolds 4937
Ta ble 3. Aver a ge In com p a tibility a n d Segr ega tion Str en gth Va lu es Ca lcu la ted Usin g øS,S-d a p ) 0.31 a n d Eq 3 w ith
Differ en t Exp on en t p Va lu es a n d In com p a tibility Va lu es Obta in ed fr om Sem iem p ir ica l Ca lcu la tion s46
PS/DEP
PS/Anth
PS/Pyr
p ) 0.17 (SSL)
p ) 0.20
øS,S-X
effN range
øS,S-X
effN range
øS,S-X
effN range
øS,S-X
effN range
øS,S-X
effN range
øS,S-X
0.11 ( 0.01
11-14
0.11 ( 0.01
11-12
0.14 ( 0.02
13-17
ø
0.13 ( 0.02
13-17
0.13 ( 0.02
12-15
0.16 ( 0.03
15-20
ø
p ) 0.25
0.15 ( 0.02
15-20
0.16 ( 0.02
15-18
0.19 ( 0.03
17-23
ø
p ) 0.30
0.17 ( 0.03
16-22
0.18 ( 0.03
16-21
0.20 ( 0.04
18-25
ø
p ) 0.50 (WSL)
topological indices26
0.22 ( 0.04
20-28
0.23 ( 0.04
20-27
0.25 ( 0.05
22-31
ø
0.09
0.10
0.13
using eqs 2 and 4 is 0.31 ( 0.06,46 locating the PS/DAP
polymers of series B in the segregation region between
øeffN ) 28 and 42.
of noncovalent interaction and the incompatibility im-
parted on the polymer segments, where multiple hy-
drogen-bonding interactions have greater impact than
aromatic stacking interactions. It is important to note
that, even within the class of aromatic stacking interac-
tions, domain periodicities are very sensitive to the
strength of the interactions, where the stronger dimer-
ization tendency of Pyr over Anth13 translates to 20-
25% increase in the determined incompatibility between
S-Pyr with styrene compared to that of S-Anth with
styrene.
Once the value of øS,S-DAP has been determined and
the segregation strength of the PS/DAP polymers of
series B were located in the intermediate segregation
regime, the other incompatibility values can be calcu-
lated relative to øS,S-DAP using eq 3 with different
exponent values that are typical to the intermediate
segregation regime. Table 3 summarizes the averaged
calculated incompatibility values of PS/DEP, PS/Anth,
and PS/Pyr and provides a comparison between five
exponent values spanning the range from 0.17 to 0.50
(SSL to WSL, respectively). The respective øeffN values
were also calculated to probe the validity of usage of
the different exponent values.
The data summarized in Table 3 indicate that as-
suming either of the extreme cases (WSL or SSL) for
the PS/DEP, PS/Anth, and PS/Pyr polymers of series B
locates them in segregation strength ranges that are
inconsistent with the assumption being made (i.e.,
assuming SSL results in øeffN values in the range 11-
17, which are in the WSL and, conversely, assuming
WSL locates the polymers well into the intermediate
segregation regime, where scaling of p ) 0.5 is unjusti-
fied). Such assumptions are expected to yield large
deviations from the true incompatibility values. Inter-
mediate exponent values (e.g., p ) 0.25-0.30) give a
more consistent picture and associate these polymers
with the intermediate segregation regime as expected
from the qualitative experimental observations (e.g.,
existence of higher order reflections). Such scaling
exponents are in accordance with the experimental
results of others (where periodicity was found to depend
of N0.8 in the intermediate segregation regime)45 and
our observation that the SAXS curves of these polymers
do not exhibit strong temperature dependence (as would
be expected from polymer bordering the order-disorder
transition45a).
Con clu sion s
A series of polymer scaffolds based on styrene and
4-chloromethylstyrene were functionalized with four
model functionalities, each featuring a unique combina-
tion of structural and chemical properties with emphasis
being given to molecular recognition capability. Char-
acterization using thermal analysis and X-ray scattering
revealed a distinct behavior pattern for each system:
the glass transition depends on both structure and
interaction capability, while microphase separation in
functionalized diblock copolymers is determined mainly
by the interaction strength and is highly sensitive to
subtle changes.
Our findings demonstrate that molecular recognition
units attached to polymers can be used to control the
solid-state structure and behavior of polymers. The
results presented in this paper clearly demonstrate the
ability to integrate molecular chemistry with solid-state
polymer physics for the prediction and manipulation of
material properties starting at the molecular level. The
approach used in this study is general (i.e., can be
applied to a wide variety of functionalities available
through organic synthesis) and can be further utilized
for the study of structure-property relationship in
polymer science. This study, thus, also lays the founda-
tion for the fundamental analysis of systems that
integrate supramolecular chemistry and polymers.
Although a few assumptions were involved in the
determination of the incompatibility values, we estimate
that our results are accurate within 25%. Even within
this error, a clear trend is observed, where functional-
ization with DEP or Anth yields a moderate incompat-
ibility, modification with Pyr results in a slightly
increased incompatibility, and attaching DAP function-
alities to the polystyrene backbone almost doubles the
incompatibility compared to polymers functionalized
with DEP or Anth. Values obtained from semiempirical
calculations (Table 3) reproduce the same trend (apart
from an apparent overestimation of the hydrogen-
bonding effect on the incompatibility in PS/DAP).46
Both experimental and theoretical values point to an
apparent correlation between the mode and the strength
Exp er im en ta l Section
Ma t er ia ls. All chemicals were reagent grade, purchased
from Aldrich or Merck with the exception of chelidamic acid
(TCI America), and were used as received. Monomers (styrene
and 4-chloromethylstyrene) were purified from the inhibitor
using a short alumina plug.
Syn th esis. P(S-co-CMS) and PS-b-P(S-co-CMS) polymer
scaffolds were synthesized via nitroxide-mediated controlled
radical polymerization.15 In the case of diblock copolymers, the
PS block was created first, purified by precipitation in metha-
nol from remaining monomer, and then polymerization of the
S/CMS mixture to yield the functionalizable block took place.
Polymerizations of the functionalizable block were stopped at
less than 10% conversion to decrease the possibility of blocki-

4938 Shenhar et al.
Macromolecules, Vol. 37, No. 13, 2004
ness that may arise from the different reactivity ratios of
styrene and CMS (0.62 and 1.12, respectively).29
1.227, 1.196, and 1.163 g/mL, respectively. Effective degrees
of polymerization (N), statistical segment lengths (a), and
volume fractions (f and x parameters) were referenced to a
constant monomer volume of styrene as calculated using
topological indices (v0 ) 161.03 Å3), which is reasonably close
to that calculated from the experimental density (164.48 Å3).29
Using 6.7 Å as the statistical segment length of styrene (aS)28
in combination with the corresponding calculated densities,
we estimated 7.2 Å for aS-Anth and aS-Pyr and 7.1 and 7.0 Å for
aS-DEP and aS-DAP, respectively.17,49 The average statistical
segment length was then calculated according to the following
relationship:42
2,6-Dip r op a m id op yr id -4-on e (DAP ). The compound was
synthesized as previously published.47
2,6-Dieth ylch elid a m a te (DEP ). The compound was syn-
thesized according to the literature procedure.48 Chelidamic
acid (0.5 g) was refluxed in 2% sulfuric acid in ethanol
overnight, concentrated in vacuo, dissolved in water, and
extracted twice with dichloromethane. Column chromatogra-
phy (SiO2, 1:1 ethyl acetate:hexanes) provided 314 mg (53%)
of the titled compound as a white crystalline solid; mp 118-
120 °C (lit.48 120-121 °C).
P olym er F u n ction a liza tion . In a typical functionalization
reaction, the parent polymer (50 mg), the functionality (1.1
CMS equiv), and K2CO3 (1.5 CMS equiv) were dissolved in 2
mL of N,N-dimethylformamide (DMF) and stirred at 70 °C
under an argon atmosphere overnight. Dropwise addition of
water resulted in immediate precipitation. The solid was
briefly sonicated in 15 mL of water, filtered, sonicated in 15
mL of methanol, filtered again, and dried under vacuum
overnight (70-90% yield). Complete conversion (within NMR
detection limits) was determined using the side-chain CH2
group resonance.
Ch a r a cter iza tion . Number-averaged molecular weights
(Mn) and polydispersity indices (PDI) of the polymers in THF
solutions were determined from gel permeation chromato-
grams (GPC) acquired on an in-house built GPC system using
PL Caliber data collection software, three-column set (Polymer
Labs, Inc.; PLgel 5 µm columns, 300 × 7.5 mm, 103, 104, and
105 Å pore size), with an RI detector (Waters 403). The system
was calibrated with respect to polystyrene standards (Polymer
Labs, Inc.). CMS content was calculated according to 1H NMR
peak integration (using a Bruker AC-200 spectrometer operat-
ing at 200.13 MHz for 1H) to an estimated error of (5% CMS
content. NMR spectra were taken in CDCl3, except from PS/
DAP(25,50%) which was measured in DMSO-d6. Glass transi-
tion temperatures were determined using differential scanning
calorimetry (DSC), performed on ca. 10 mg samples under
continuous nitrogen purge (50 mL/min) on a TA Instruments
DSC 2910. Data represent the second heating cycles using a
heating scan rate of 10 °C/min. Infrared spectra were recorded
using either KBr plates or a solution cell on a MIDAC 2000
FTIR spectrometer. Fluorescence spectra of dilute solutions
(in a 1 mm quartz cuvette) or of thin films (deposited from
solution onto glass slides and annealed at 150 °C for 2 h) were
acquired on a Shimadzu RF-5301 PC spectrofluorophotometer.
Samples were excited at 350 nm.
-1/2
1 - f
f
a )
+
2
2
2
(
)
aS
xaS-X + (1 - x)aS
For comparison with experimental results, interaction
parameters were calculated from cohesive energies that were
also calculated using the topological indices methods, which
exhibit R2 ) 0.995 correlation with experimental values.26
Ack n ow led gm en t. R.S. is in debt to Prof. Marc A.
Hillmyer, Prof. Thomas P. Russell, and Matthew J .
Misner for helpful discussions and assistance. Financial
support from the NSF [CHE-0213354 (V.R.)] and MR-
SEC (DMR 0213695) is gratefully acknowledged. R.S.
thanks The Fulbright Foundation for a postdoctoral
fellowship.
Su p p or tin g In for m a tion Ava ila ble: GPC traces and
NMR spectra of all discussed polymers. This material is
available free of charge via the Internet at http://pubs.acs.org.
Refer en ces a n d Notes
(1) See, for example: Szwarc, M.; van Beylen, M. Ionic Polym-
erization and Living Polymers; Chapman & Hall: New York,
1993. Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34,
18.
(2) Thurn-Albrecht, T.; Schotter, J .; Ka¨stle, C. A.; Emley, N.;
Shibauchi, T.; Krusin-Elbaum, L.; Guarini, K.; Black, C. T.;
Tuominen, M. T.; Russell, T. P. Science 2000, 290, 2126.
Chan, V. Z.-H.; Hoffman, J .; Lee, V. Y.; Iatrou, H.; Avgeropou-
los, A.; Hadjichristidis, N.; Miller, R. D.; Thomas, E. L.
Science 1999, 286, 1716. Park, M.; Harrison, C.; Chaikin, P.
M.; Register, R. A.; Adamson, D. H. Science 1997, 276, 1401.
(3) Fredrickson, G. H.; Bates, F. S. Annu. Rev. Mater. Sci. 1996,
26, 501. Bates, F. S.; Fredrickson, G. H. Annu. Rev. Phys.
Chem. 1990, 41, 525.
(4) Ruokolainen, J .; Ma¨kinen, R.; Torkkeli, M.; Ma¨kela¨, T.;
Serimaa, R.; ten Brinke, G.; Ikkala, O. Science 1998, 280,
557. Ikkala, O.; ten Brinke, G. Science 2002, 295, 2407.
(5) Grzybowski, B.; Whitesides, G. M. Science 2002, 295, 2418.
Lehn, J .-M. Supramolecular Chemistry, Concepts and Per-
spectives; VCH: Weinheim, Germany, 1995. Whitesides, G.
M.; Mathias, J . P.; Seto, C. T. Science 1991, 254, 1312.
Whitesides, G. M.; Simanek, E. E.; Mathias, J . P.; Seto, C.
T.; Chin, D. N.; Mammen, M.; Gordon, D. M. Acc. Chem. Res.
1995, 28, 37. Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L.
S.; Huggins, K. E.; Keser, M.; Amstutz, A. Science 1997, 276,
384.
(6) Sijbesma, R. P.; Beijer, F. H.; Brunsveld, L.; Folmer, B. J .
B.; Hirschberg, J . H. K. K.; Lange, R. F. M.; Lowe, J . K. L.;
Meijer, E. W. Science 1997, 278, 1601. Keizer, H. M.;
Sijbesma, R. P.; J ansen, J . F. G. A.; Pasternack, G.; Meijer,
E. W. Macromolecules 2003, 36, 5602. Hirschberg, J . H. K.
K.; Brunsveld, L.; Ramzi, A.; Vekemans, J . A. J . M.; Sijbesma,
R. P.; Meijer, E. W. Nature (London) 2000, 407, 167. Folmer,
B. J . B.; Sijbesma, R. P.; Versteegen, R. M.; van der Rijt, J .
A. J .; Meijer, E. W. Adv. Mater. 2000, 12, 874. Lange, R. F.
M.; Van Gurp, M.; Meijer, E. W. J . Polym. Sci., Polym. Chem.
1999, 37, 3657. Lange, R. F. M.; Meijer, E. W. Macromolecules
1995, 28, 782. Zubarev, E. R.; Pralle, M. U.; Li, L. M.; Stupp,
S. I. Science 1999, 283, 523. Zubarev, E. R.; Pralle, M. U.;
Sone, E. D.; Stupp, S. I. Adv. Mater. 2002, 14, 198.
(7) Gohy, J . F.; Lohmeijer, B. G. G.; Schubert, U. S. Chem.s
Eur. J . 2003, 9, 3472. Lohmeijer, B. G. G.; Schubert, U. S. J .
Polym. Sci., Polym. Chem. 2003, 41, 1413. Meier, M. A. R.;
Sm a ll-An gle X-r a y Sca tter in g (SAXS). To avoid kinetic
entrapment by solvent evaporation effects, solid polymer
samples (ca. 10 mg) in the precipitated powder form were
annealed at 150 °C under vacuum for 2 days and quenched to
room temperature. Cu KR X-rays (1.54 Å) were generated in
an Osmic MaxFlux source with a confocal multilayer optic
(OSMIC, Inc.). Images were taken with a Molecular Metrology,
Inc., camera consisting of a three pinhole collimation system,
150 cm sample-to-detector distance (calibrated using silver
behenate), and a 2-dimensional, multiwire proportional detec-
tor (Molecular Metrology, Inc.). The entire X-ray path length
was evacuated from the optic to the detector in order to reduce
the background from air scattering. This setup allowed
neglecting the correction for background scattering as proved
by experiment. Two-dimensional images were reduced to the
one-dimensional form using angular integration. Scattering
vectors (q) were calculated from the scattering angles (θ) using
q ) 4π sin θ/λ, and domain periodicities (D) were calculated
from Gaussian fits to the principal scattering maxima of the
Lorentz-corrected intensities using D ) 2π/q.
Sem iem p ir ica l Ca lcu la tion s. All molar and van der
Waals volumes (of the modified styrene monomers as well as
that of styrene) were calculated using topological indices,26
a
method that is derived from graph theory and is considered
to give remarkably reliable predictions due to the excellent
correlation (R2 ) 0.998) found with experimental values. Mass
densities of the homopolymers of PS/Pyr, PS/Anth, PS/DEP,
and PS/DAP calculated from the molar volumes are 1.247,

Macromolecules, Vol. 37, No. 13, 2004
Macromolecular Scaffolds 4939
Lohmeijer, B. G. G.; Schubert, U. S. Macromol. Rapid
Commun. 2003, 24, 852. Gohy, J . F.; Lohmeijer, B. G. G.;
Varshney, S. K.; Schubert, U. S. Macromolecules 2002, 35,
7427. Yamauchi, K.; Lizotte, J . R.; Long, T. E. Macromol-
ecules 2003, 36, 1083. Yamauchi, K.; Lizotte, J . R.; Hercules,
D. M.; Vergne, M. J .; Long, T. E. J . Am. Chem. Soc. 2002,
124, 8599. Yamauchi, K.; Lizotte, J . R.; Long, T. E. Macro-
molecules 2002, 35, 8745.
Windle, A. H. J . Appl. Polym. Sci. 1994, 53, 561. Dang, T.
D.; Mather, P. T.; Alexander, M. D., J r.; Grayson, C. J .; Houtz,
M. D.; Spry, R. J .; Arnold, F. E. J . Polym. Sci., Polym. Chem.
2000, 38, 1991. Stengersmith, J . D.; Henry, R. A.; Hoover, J .
M.; Lindsay, G. A.; Nadler, M. P.; Nissan, R. A. J . Polym.
Sci., Polym. Chem. 1993, 31, 2899. Pellice, S. A.; Fasce, D.
P.; Williams, R. J . J . J . Polym. Sci., Polym. Phys. 2003, 41,
1451. Barbeau, P.; Gerard, J . F.; Magny, B.; Pascault, J . P.
J . Polym. Sci., Polym. Phys. 2000, 38, 2750. Schmaljohann,
D.; Haussler, L.; Potschke, P.; Voit, B. I.; Loontjens, T. J . A.
Macromol. Chem. Phys. 2000, 201, 49. Gestoso, P.; Brisson,
J . Comput. Theor. Polym. Sci. 2001, 11, 263.
(8) Yamauchi, K.; Lizotte, J . R.; Long, T. E. Macromolecules
2003, 36, 1083. Yamauchi, K.; Lizotte, J . R.; Hercules, D. M.;
Vergne, M. J .; Long, T. E. J . Am. Chem. Soc. 2002, 124, 8599.
Yamauchi, K.; Lizotte, J . R.; Long, T. E. Macromolecules
2002, 35, 8745.
(9) Pollino, J . M.; Stubbs, L. P.; Weck, M. J . Am. Chem. Soc.
2004, 126, 563. Stubbs, L. P.; Weck, M. Chem.sEur. J . 2003,
9, 992.
(10) Boal, A. K.; Ilhan, F.; DeRouchey, J . E.; Thurn-Albrecht, T.;
Russell, T. P.; Rotello, V. M. Nature (London) 2000, 404, 746.
Frankamp, B. L.; Uzun, O.; Ilhan, F.; Boal, A. K.; Rotello, V.
M. J . Am. Chem. Soc. 2002, 124, 892.
(11) Das, K.; Penelle, J .; Rotello, V. M. Langmuir 2003, 19, 3921.
Duffy, D. J .; Das, K.; Hsu, S. L.; Penelle, J .; Rotello, V. M.;
Stidham, H. D. J . Am. Chem. Soc. 2002, 124, 8290.
(12) (a) Chino, K.; Ashiura, M. Macromolecules 2001, 34, 9201.
(b) de Lucca Freitas, L.; J acobi, M. M.; Gonc¸alves, G.; Stadler,
R. Macromolecules 1998, 31, 3379. (c) de Lucca Freitas, L.
L.; Stadler, R. Macromolecules 1987, 20, 2478.
(13) Gonzalez, C.; Lim, E. C. J . Phys. Chem. A 2003, 107, 10105.
(14) For an example where an attached mesogen creates a sense
of a diblock copolymer, see: Sentenac, D.; Demirel, A. L.; Lub,
J .; de J eu, W. H. Macromolecules 1999, 32, 3235.
(15) Benoit, D.; Chaplinski, V.; Braslau, R.; Hawker, C. J . J . Am.
Chem. Soc. 1999, 121, 3904. Harth, E.; Hawker, C. J .; Fan,
W.; Waymouth, R. M. Macromolecules 2001, 34, 3856.
Hawker, C. J . J . Am. Chem. Soc. 1994, 116, 11185.
(16) In the notation of block copolymers, z corresponds to the
molar fraction of the functionality in the functionalized block
only, and the Mn’s given relate to the PS and functionalized-
PS blocks in the corresponding parent polymer scaffold.
(17) Shenhar, R.; Sanyal, A.; Uzun, O.; Rotello, V. M. Macromol-
ecules 2004, 37, 92.
(18) Ilhan, F.; Gray, M.; Blanchette, K.; Rotello, V. M. Macromol-
ecules 1999, 32, 6159.
(19) Winnik, F. M. Chem. Rev. 1993, 93, 587.
(20) Winnik, F. M.; Tamai, N.; Yonezawa, J .; Nishimura, Y.;
Yamazaki, I. J . Phys. Chem. 1992, 96, 1967.
(21) Farid, S.; Martic, P. A.; Daly, R. C.; Thompson, D. R.; Specht,
D. P.; Hartman, S. E.; Williams, J . L. R. Pure Appl. Chem.
1979, 51, 241.
(22) Gray, M.; Cuello, A. O.; Cooke, G.; Rotello, V. M. J . Am. Chem.
Soc. 2003, 125, 7882. Cooke, G.; Rotello, V. M. Chem. Soc.
Rev. 2002, 31, 275. Niemz, A.; Rotello, V. M. Acc. Chem. Res.
1999, 32, 44.
(23) Katritzky, A. R.; Ghiviriga, I. J . Chem. Soc., Perkin Trans. 2
1995, 1651.
(24) Beijer, F. H.; Sijbesma, R. P.; Vekemans, J . A. J .; Meijer, E.
W.; Kooijman, H.; Spek, A. L. J . Org. Chem. 1996, 61, 6371.
(25) Donth, E. The Glass Transition: Relaxation Dynamics in
Liquids and Disordered Materials; Springer: New York,
2001.
(26) Bicerano, J . Prediction of Polymer Properties, 3rd ed.; Marcel
Dekker: New York, 2002.
(28) Physical Properties of Polymers Handbook; Mark, J . E., Ed.;
American Institute of Physics: Woodbury, NY, 1996.
(29) Polymer Handbook, 4th ed.; Brandrup, J ., Immergut, E. H.,
Grulke, E. A., Eds.; Wiley-Interscience: New York, 1999.
(30) The slightly lower glass transition temperatures observed for
the (28:13, 40%) block copolymers compared to the analogous
(25, 50%) random copolymers is associated with the slightly
lower functionality content in the block copolymers.17
(31) Strobl, G. The Physics of Polymers; Springer: Berlin, 1996.
(32) Doi, M. Introduction to Polymer Physics: Clarendon Press:
Oxford, 1996.
(33) J ablonski, E. L.; Gorga, R. E.; Narasimhan, B. Polymer 2003,
44, 729. Gorga, R. E.; J ablonski, E. L.; Thiyagarajan, P.;
Seifert, S.; Narasimhan, B. J . Polym. Sci., Part B: Polym.
Phys. 2002, 40, 255. van Ekenstein, G. O. R. A.; Meyboom,
R.; ten Brinke, G.; Ikkala, O. Macromolecules 2000, 33, 3752.
Oudhuis, A. A. C. M.; ten Brinke, G.; Karasz, F. E. Polymer
1993, 34, 1991. Salomons, W.; ten Brinke, G.; Karasz, F. E.
Polym. Commun. 1991, 32, 185.
(34) Vavasour, J . D.; Whitmore, M. D. Macromolecules 1992, 25,
5477.
(35) Leibler, L. Macromolecules 1980, 13, 1602.
(36) Matsen, M. W.; Bates, F. S. Macromolecules 1996, 29, 1091.
(37) Shull, K. R. Macromolecules 1992, 25, 2122. Olvera de la
Cruz, M.; Mayes, A. M. Macromolecules 1991, 24, 3975.
(38) Helfand, E.; Wasserman, Z. R. Macromolecules 1976, 9, 879.
Ohta, T.; Kawasaki, K. Macromolecules 1986, 19, 2621.
(39) Semenov, A. N. Sov. Phys. J ETP 1985, 61, 733. Semenov, A.
N. Macromolecules 1993, 26, 6617.
(40) Melenkevitz, J .; Muthukumar, M. Macromolecules 1991, 24,
4199.
(41) Hasegawa, H.; Tanaka, H.; Yamasaki, K.; Hashimoto, T.
Macromolecules 1987, 20, 1651. Hashimoto, T.; Shibayama,
M.; Kawai, H. Macromolecules 1980, 13, 1237.
(42) Ren, Y.; Lodge, T. P.; Hillmyer, M. A. Macromolecules 2000,
33, 866. Ren, Y.; Lodge, T. P.; Hillmyer, M. A. Macromolecules
2002, 35, 3889.
(43) The absence of distinct Bragg reflections in PS/DEP, PS/Anth,
and PS/Pyr of the (27:13, 17%) composition does not arise
from low electron density contrast, as PS/DAP(27:13, 17%)
does exhibit a distinct reflection, while the calculated electron
densities for all four functionalities vary within less than 2%.
(44) All precursors to polymers of series B were synthesized from
the same batch of PS block, with the same styrene/CMS
mixture composition (i.e., comonomer quantities); thus, the
differences in length between the functionalized blocks of
these polymers resulted only from different polymerization
times.
(45) (a) Almdal, K.; Rosedale, J . H.; Bates, F. S.; Wignall, G. D.;
Fredrickson, G. H. Phys. Rev. Lett. 1990, 65, 1112. (b)
Hadziioannou, G.; Skoulios, A. Macromolecules 1982, 15, 258.
(46) Semiempirical calculations using topological indices (see
Experimental Section and ref 17) estimate øS,S-DAP from
solubility parameters by 0.58, which is within the same order
of magnitude of that of the experimental determination.
(47) Ilhan, F.; Gray, M.; Rotello, V. M. Macromolecules 2001, 34,
2597.
(27) See, for example: Sunder, A.; Bauer, T.; Mulhaupt, R.; Frey,
H. Macromolecules 2000, 33, 1330. Yuan, Y.; Shoichet, M. S.
Macromolecules 1999, 32, 2669. Miyoshi, T.; Takegoshi, K.;
Terao, T. Macromolecules 1999, 32, 8914. Dorr, M.; Zentel,
R.; Dietrich, R.; Meerholz, K.; Brauchle, C.; Wichern, J .;
Zippel, S.; Boldt, P. Macromolecules 1998, 31, 1454. Parthiban,
A.; Le Guen, A.; Yansheng, Y.; Hoffmann, U.; Klapper, M.;
Mu¨llen, K. Macromolecules 1997, 30, 2238. Kuo, S.-W.; Kao,
H.-C.; Chang, F.-C. Polymer 2003, 44, 6873. Xua, H.; Kuo,
S.-W.; Lee, J .-S.; Chang, F.-C. Polymer 2002, 43, 5117.
Wirasate, S.; Dhumrongvaraporn, S.; Allen, D. J .; Ishida, H.
J . Appl. Polym. Sci. 1998, 70, 1299. Gao, H.; Harmon, J . P.
J . Appl. Polym. Sci. 1998, 64, 507. He, C.; Griffin, A. C.;
(48) Markees, D. G. J . Org. Chem. 1964, 29, 3120.
(49) The larger values calculated for the functionalized styrenes
compared to that of styrene are in accord with increased
stiffness induced by the added bulk.
MA0495590