Synthesis and thermal characterization of precision poly(ethylene-co-vinyl amine) copolymers

Article abstract of DOI:10.1021/ma202233a

A structural investigation of linear ethylene-co-vinyl amine (EVAm) copolymers having a primary amine branch on every 9th, 15th, 19th, or 21st carbon along the ethylene backbone has been completed using step polymerization chemistry. Acyclic diene metathesis (ADMET) polymerization has been used with symmetrical α,ω dienes containing protected amine groups to afford polymers with exact primary structures and constant methylene run lengths between branches. The effects of subtle structural changes such as the ethylene run lengths between amine branches can be observed and used to correlate structure property relationships. NMR and FT-IR techniques are used to characterize and verify the excellent structural control this synthetic approach provides over traditional chain polymerization techniques. Thermal decomposition of these copolymers is shown to additionally support polymer structure while differential scanning calorimetry demonstrates crystallinity in the polymers with an amine on every 15th and 21st carbon, whereas the polymer with an amine on every ninth carbon is amorphous. Variations of the physical and spectral properties are discussed as a consequence of the amine branch spacing, protection, and saturation of the ethylene backbone.

Full text of DOI:10.1021/ma202233a

Article
pubs.acs.org/Macromolecules
Synthesis and Thermal Characterization of Precision Poly(ethylene-
co-vinyl Amine) Copolymers
James K. Leonard, Yuying Wei, and Kenneth B. Wagener*
The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, University of Florida, Gainesville,
Florida 32611, United States
ABSTRACT: A structural investigation of linear ethylene-co-
vinyl amine (EVAm) copolymers having a primary amine
branch on every 9th, 15th, 19th, or 21st carbon along the
ethylene backbone has been completed using step polymer-
ization chemistry. Acyclic diene metathesis (ADMET)
polymerization has been used with symmetrical α,ω dienes
containing protected amine groups to afford polymers with
exact primary structures and constant methylene run lengths
between branches. The effects of subtle structural changes
such as the ethylene run lengths between amine branches can
be observed and used to correlate structure property relationships. NMR and FT-IR techniques are used to characterize and
verify the excellent structural control this synthetic approach provides over traditional chain polymerization techniques. Thermal
decomposition of these copolymers is shown to additionally support polymer structure while differential scanning calorimetry
demonstrates crystallinity in the polymers with an amine on every 15th and 21st carbon, whereas the polymer with an amine on
every ninth carbon is amorphous. Variations of the physical and spectral properties are discussed as a consequence of the amine
branch spacing, protection, and saturation of the ethylene backbone.
involved two main precursors: tert-butyl N-vinylcarbamate
(TBNVC)9 and vinylformamide (VFA) monomers.10,11 BASF,
the largest commercial producer of PVAm, has utilized
vinylformamide (VFA) with the subsequent hydrolysis of its
amide side chains to make PVAm.
Of all the potential copolymers that can be made with
vinylamine, those with ethylene as the comonomer are of
particular interest. Poly(ethylene-co-vinyl amine) (PEVAm)
polymers, with ethylene:vinylamine molar ratios of at least 1:1,
are ideal for use as flocculants in water clarification. The molar
ratio of these copolymers is modified by monomer addition
under high-pressure conditions via radical chemistry. The ideal
ethylene:vinylamine ratio in these materials is 2:1 to 4:1.12
Within this preferred range, the desired physical and chemical
properties imparted by the amine units are preserved, while the
cost of the polymers is markedly lowered by the presence of the
more economical ethylene units.12
Other than the usual backbone defects elicited by the radical
chain polymerization of these materials, irregularities encoun-
tered in PEVAm materials come from both the acid and base
hydrolysis of the poly(N-vinylformamide). Acid hydrolysis can
proceed via transiently formed amidine rings, but is unable to
surpass the 80% level due to repulsions among the protonated
amine side chains.11 Basic hydrolysis can be carried out
completely, but Spange10 and Bortel11 have both observed the
INTRODUCTION
■
Ethylene-co-vinyl amine polymers (PEVAm) have several
desirable characteristics and numerous commercial applications.
The primary amine functionality along the ethylene backbone is
a highly reactive site that can be utilized for derivatization and
cross-linking. In the protonated form, the cationic charge
density of the ammonium ion makes it useful in ionomer
applications.1 In addition, the ability of amines to chelate allow
them to form complexes with various metal ions2,3 and to serve
as support scaffolds for enzymes.4 Considering the many
potential applications of these materials, it is important to have
an understanding of their primary structure's relationship to
physical properties. However, structure−property information
of this type has not been readily available or even known.
The lack of fundamental studies can be attributed partly to
synthetic difficulties, which have also limited the applications of
PEVAm. The copolymerization of ethylene with vinyl amine
type monomers is a difficult task due to both the large reactivity
ratio disparity of the two vinyl monomers and the tendency of
the vinyl amine to act as an efficient chain-transfer agent during
radical and cationic polymerization.5 The simplest precursor
monomer for synthesis of polyvinylamine (PVAm), vinyl
amine, does not exist in the free state because it tautomerizes
to the acetaldehyde imine.5 This monomer lability necessitates
the synthesis of PVAm indirectly from an intermediate
polymer, a synthetic approach similar to that used with
poly(vinyl alcohol) (PVA).5
Although PVAm has been synthesized in numerous ways,6−8
preparation of PVAm via radical chemistry with minimal
structural defects and reasonably high molecular weights has
Received: October 6, 2011
Revised: November 30, 2011
Published: December 19, 2011
© 2011 American Chemical Society
671
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
long time scans from these nonlabeled materials were conducted in
order to achieve good signal-to-noise ratios.
elimination of ammonia as noted by elemental analysis and the
perceptible smell during the hydrolysis.
Differential scanning calorimetry (DSC) was performed on a TA
Instruments Q1000 equipped with a liquid nitrogen cooling accessory
and calibrated using sapphire and high purity indium metal. All
samples were prepared in hermetically sealed pans (4−7 mg/sample)
and were referenced to an empty pan. A scan rate of 10 °C per minute
was used. Melting temperatures were taken as the peak of the melting
transition, glass transition temperatures as the midpoint of a step
change in heat capacity. Thermal experiments were conducted as
follows: samples were heated through the melt to erase thermal
history, followed by cooling at 10 °C per minute to −150 °C, and then
heated through the melt at 10 °C per minute. Data reported reflects
this second heating scan.
Premonomer Amine Diene Synthesis. Magnesium (4.89 g,
0.20 mol) was added to a 500 mL three-necked flask equipped with a
reflux condenser and an addition funnel. The reaction vessel was
backfilled three times with Ar and flame-dried after each backfill. Dry
THF (100 mL) was added, followed by the addition of 5-bromo-1-
pentene (25.0 g, 0.17 mol) dropwise via syringe. The solution was
refluxed for 2 h to completely form the Grignard. Ethyl formate (5.64 g,
0.076 mol) in 30 mL THF was added dropwise to the cooled mixture
(0 °C), and the solution was allowed to warm slowly to room tem-
perature and then refluxed for 21 h. Hydrochloric acid (1M, 100 mL)
was added, and the solution was extracted with ether (3 × 25 mL),
washed with 1 M HCl (1 × 30 mL), and washed with brine (3 × 20 mL).
The solution was dried over MgSO4, followed by evaporation of the
solvent to yield 14.18 g of the crude alcohol.
By taking advantage of step polymerization chemistry offered
by acyclic diene metathesis (ADMET), our research group has
been able to avoid the random nature of addition polymer-
izations, as well as the unwanted side reactions often observed
in radical polymerizations of vinyl monomers. This mild
polymerization chemistry also avoids the defects usually
imparted by catalysts during chain propagation processes.
These defects, in either small or large amounts, can have
profound effects on the macromolecule’s material behavior and
thermal response.
Both Breitenkamp13 and Masuda14 have utilized ring-
opening metathesis polymerization (ROMP) to prepare
amine-functionalized polymers. Herein, we report the synthesis
and thermal characterization of a family of four linear EVAm
copolymers with amine branches precisely spaced along the
polyethylene backbone at intervals of every 9th, 15th, 19th, or
21st carbon. Their preparation has been accomplished using
ADMET chemistry, which assures that the branches are set at
specific, not random, intervals along the backbone, generating
polymers incapable of being made by other method-
ologies.15−21 Primary structural analysis has been achieved by
1H and 13C NMR and FT-IR techniques, and detailed
calorimetry data are presented to demonstrate the morpho-
logical differences arising from the combined effects of branch
frequency and the regular distribution of amine branches.
To a 500 mL round-bottom flask equipped with an addition funnel
were added pyridinium chlorochromate (PCC) (26.0 g, 0.12 mol),
Celite (equal weight to crude alcohol), and methylene chloride (100 mL)
followed by the addition of the crude alcohol (1 equiv). The reaction
was stirred for 4 h at room temperature, diethyl ether (200 mL) was
added, and the mixture was filtered through a pad of silica gel. Solvent
evaporation yielded 13.0 g of the crude ketone.
EXPERIMENTAL SECTION
■
Materials. Reagents and chemicals were used as received from
Aldrich Chemical Co. unless otherwise noted. Diethyl ether and THF
were used as dry solvents from the Aldrich keg system and dried over
To a 500 mL round-bottom flask was added the crude ketone, dry
methanol (225 mL), ammonium acetate (60 g, 0.78 mol), sodium
cyanoborohydride NaCNBH3 (25 g, 0.40 mol), and a spatula tip of
́
4 Å sieves. The second generation Grubbs catalyst (tricyclohexyl-
phosphine[1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-
ylidene][benzylidene]ruthenium(IV) dichloride) was synthesized and
used as previously described by Grubbs et al.22
́
crushed 4 Å molecular sieves; the mixture was refluxed for 48 h under
N . The crushed molecular sieves were filtered via Buchner filtration
̈
2
Instrumentation and Analysis. 1H NMR and 13C NMR spectra
were recorded on a Varian Associates Mercury 300 spectrometer.
Chemical shifts for 1H and 13C NMR were referenced to residual
signals from CDCl3 (1H = 7.24 ppm and 13C = 77.23 ppm) with 0.03%
v/v TMS as an internal reference. High resolution mass spectra
(HRMS) were obtained on a Finnegan 4500 gas chromatograph/mass
spectrometer using the chemical ionization mode. IR data was
obtained using a Perkin-Elmer Spectrum One FT-IR outfitted with a
LiTaO3 detector, measurements were automatically corrected for
water and carbon dioxide. FT-IR polymer samples were prepared by
solution-casting a thin film from THF onto a KBr salt plate.
Gel permeation chromatography (GPC) of polymers was
performed at 40 °C using a Waters Associates GPCV2000 liquid
chromatography system with an internal differential refractive index
detector (DRI) and two Waters Styragel HR-4E columns (10 μm PD,
7.8 ID, 300 mm length) using HPLC grade tetrahydrofuran as the
mobile phase at a flow rate of 1.0 mL/min. Injection volumes of 220.5 μL
were made at 0.05−0.07 w/v sample concentrations. Retention
times were calibrated against a minimum of nine narrow molecular
weight polystyrene standards purchased from Polymer Laboratories
(Amherst, MA).
and deionized water (200 mL) was added to the filtrate, followed by
extraction with diethyl ether (3 × 50 mL). The organic layer was
washed with 1 M NaOH (2 × 50 mL) and brine (2 × 30 mL) and
dried over MgSO4. The solution was concentrated to a brown viscous
oil, which was purified by flash column chromatography using a 3:1:1
(hexane:ethyl acetate:methanol) mobile phase yielding 9.28 g of the
desired 3,3NH2 product for an overall yield of 73%.
1-Undec-10-enyl-dodec-11-enylamine (3,3NH2). 1H NMR (300
MHz, CDCl3): δ 1.15−1.70 (m, 8H), 2.01−2.15 (br,4H), 2.65−2.76
(br, 1H), 4.90−5.10 (m, 4H), 5.75−5.90 (m, 2H). 13C NMR (75
MHz, CDCl3): δ 25.87, 34.29, 37.84, 51.45, 114.95, 139.19.
Heptadeca-1,16-dien-9-amine (6,6NH2). This premonomer was
in limited supply and is extremely valuable so it was used in situ to
directly make the Boc-protected monomer.
Tricosa-1,22-dien-12-amine (9,9NH2). The 9,9NH2 was synthe-
sized as described above using 11-bromo-1-undecene (25.0 g, 0.106
mol) instead of 5-bromo-1-pentene. After purification, a final yield of
1
48% (13.0 g) was obtained. H NMR (300 MHz, CDCl3): δ 1.15−
1.45 (br, 32H), 2.05 (q, 4H), 2.65−2.75 (br, 1H), 4.88−5.05 (m, 4H),
5.72−5.38 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 26.39, 29.20,
29.41, 29.76, 29.84, 29.90, 30.07, 34.08, 38.02, 51.50, 114.36, 139.50.
1-Dec-9-enyl-undec-10-enylamine (8,8NH2). Synthesis was per-
formed using a modified procedure by Zantour and co-workers.39 To a
500 mL three-neck round-bottom flask equipped with a reflux
condenser and an addition funnel was added 10-undecenoyl chloride
(20.27 g, 100 mmol) and dry diethyl ether (150 mL). The solution
was cooled to 0 °C, and triethylamine (18.21 g, 180 mmol) was added
dropwise, instantly forming white triethylamonium chloride salts. The
reaction mixture was warmed to room temperature and stirred for 24 h,
Solid-State NMR (SS-NMR) spectra were performed at the Max
Planck Institute for Polymer Research (MPIP) in Mainz, Germany
using a Bruker DSX 7.05 T instrument at 21.7 MHz for 15N employing
a magic angle spinning (MAS) frequency of 10 kHz. The 15N cross-
polarization from 1H was conducted using a contact angle of 7 ms and
1
a high-power H decoupling two-pulse phase modulation (TPPM) of
100 kHz. The 15N spectra were referenced to the 15NO3 in 15N-enriched
NH4NO3. All spectra were acquired from a 4 mm rotor at room tem-
perature. Because of the low natural abundance of nitrogen-15 (0.37%),
followed by Buchner filtration of the salts and evaporation to yield
̈
672
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
the liquid intermediate β-lactone. Deionized water (100 mL) and
NaOH (8.80 g, 2.10 mol) were added, and the mixture was refluxed
for 12 h. The solution was acidified with 1 M HCl and extracted with
diethyl ether (3 × 50 mL). The combined organic layers were washed
with 1 M HCl (2 × 20 mL) and brine (2 × 20 mL). After drying over
MgSO4 and recrystallizing from MeOH, 13.15 g of the pure ketone
was obtained. The ketone was converted to the amine using the same
methodology as described with the 3,3NH2 and 9,9NH2 syntheses.
CHNO: C, 76.60; H, 12.11; N, 3.44. Found: C, 76.58; H, 12.26; N,
3.47.
tert-Butyl Tricosa-1,22-dien-12-ylcarbamate 9,9NHBoc (4).
1
Monomer is a waxy white solid that melts at 46 °C. H NMR (300
MHz, CDCl3): δ 1.22−1.40 (br, m, 32H), 1.41 (s, 9H), 2.01 (q, 4H),
3.49 (br, 1H), 4.20 (br, d, 1H), 4.91 (m, 4H), 5.78 (m, 2H). 13C NMR
(75 MHz, CDCl3): δ 26.07, 27.63, 28.66, 29.15, 29.34, 29.68, 29.74,
29.80, 34.02, 35.84, 50.90, 78.95, 114.30, 139.43, 155.94. FT-IR (KBr
pellet): 3446, 3349, 3077, 2977, 2927, 2855, 1820, 1705, 1641, 1503,
1456, 1415, 1390, 1365, 1247, 1174, 1049, 992, 909, 867, 780, 750,
722, 636, 552, 464 cm−1. EI/HRMS [2M +1]: calcd for C28H53NO2,
871.8225; found, 871.8195. Anal. Calcd for CHNO: C, 77.18; H,
12.26; N, 3.21. Found: C, 77.24; H, 12.27; N, 3.25.
1
The overall yield for the two steps was 58%. H NMR (300 MHz,
CDCl3): δ 1.18−1.62 (br, 28H), 2.04 (q, 4H), 2.80−2.94 (m, br, 1H),
4.03−4.54 (br, 2H), 4.88−5.07 (m, 4H), 5.71−5.91 (m, 2H). 13C
NMR (75 MHz, CDCl3): δ 26.52, 29.34, 29.54, 29.88, 30.01, 30.20,
34.21, 38.18, 41.61, 114.46, 139.50.
General Fmoc Protection of the Amine Dienes. To a dry
500 mL round-bottom flask were added 150 mL of dry THF, 50 mL of
dry pyridine, and Fmoc−Cl (1.0 g, 3.90 mmol) under argon. Then,
9,9NH2 (1 g, 3.25 mmol) was slowly added over 0.5 h and the reaction
was allowed to stir at room temperature for an additional 2 h. After
2 h, 100 mL of ether was added to the reaction and it was extracted
with 1 M HCl (2 × 50 mL) and brine (2 × 50 mL). The protected
amine solution was dried over MgSO4 followed by rotary evaporation
to yield the 9,9NHFmoc product. The 9,9NHFmoc was purified via
column chromatography using ethyl acetate:hexane (3:2).
(9H-Fluoren-9-yl)methyl Henicosa-1,20-dien-11-ylcarbamate
(9,9NHFmoc). 1H NMR (300 MHz, CDCl3): δ 7.75 (d, 2H), 7.61
(d, 2H), 7.40 (t, 2H), 7.28 (t, 2H), 5.82 (m, 2H), 4.94 (m, 4H), 4.40
(d, 2H), 4.23 (t, 1H), 2.04 (m, 4H), 1.15−1.45 (br, 28H). EI/HRMS
[M + 1]: calcd for C36H51NO2, 530.3998; found, 530.4006.
General ADMET Polymerization Procedure for Symmetrical
Boc Amine Monomers. Monomer was transferred into a dry 25 mL
Schlenk tube equipped with a stir bar and glass stopcock and dried by
heating the vessel in an oil bath at 50 °C under full vacuum (10−3
mmHg) for 24 h. After 24 h, the reaction vessel was backfilled with
argon and first-generation Grubbs’ Ru catalyst (200:1/monomer:-
catalyst) was added. The full vacuum was placed back on the
polymerization reaction after 0.5 h. Additional catalyst was added 60 h
into the polymerization to ensure maximum possible couplings. The
polymerization reaction was monitored closely by 1H NMR to confirm
that no remaining terminal olefin was present. Upon completion, the
reaction was quenched by opening the flask and adding 25 mL of
toluene and 1 mL of ethyl vinyl ether. The polymer was purified by
precipitation of the polymer solution into 1.5 L of cold methanol. The
polymer was then filtered and dried for characterization.
General Boc Protection of the Amine Dienes. To a dry 500
mL round-bottom flask was charged 150 mL dry THF and the
appropriate amine (2.5 g) under argon. A syringe was used to add the
Boc anhydride (1 M in THF, 1 equiv) over 15 min at room tem-
perature. The reaction was allowed to stir for 24 h and was monitored
by TLC (ethyl acetate: hexane, 1:19) for disappearance of the starting
material amine. At the end of the 24 h reaction period, 100 mL of
ether was added and the solution was extracted with water (1 × 50 mL),
NaHCO3 (2 × 50 mL), and brine (2 × 50 mL). The washed solution
was dried over MgSO4 followed by rotary evaporation to yield the Boc
protected product. The monomer was purified via column
chromatography using ethyl acetate:hexane (1:19).
Polymerization of tert-Butyl Undeca-1,10-dien-6-ylcarbamate
3,3NHBoc (5). 1H NMR (300 MHz, CDCl3): δ 1.18−1.48 (br,
17H), 1.92 (br, 4H), 3.48 (br, 1H), 4.26 (br, 1H), 5.24−5.40 (br, 2H).
13C NMR (75 MHz, CDCl3): δ 26.01, 27.26, 28.63, 29.18, 29.85,
32.64, 35.31, 50.63, 78.92, 129.95, 130.43, 155.88. FT-IR (KBr pellet):
3443, 3341, 2977, 2931, 2857, 2248, 1691, 1523, 1456, 1391, 1365,
1248, 1174, 1056, 968, 912, 867, 779, 734, 647, 462 cm−1.
Polymerization of tert-Butyl Heptadeca-1,16-dien-9-ylcarbamate
6,6NHBoc (6). 1H NMR (300 MHz, CDCl3): δ 1.26 (br, 14H), 1.41
(s, 9H), 1.96 (br, 4H), 3.49 (br, 1H), 4.21 (br, 1H), 5.28−5.5.37 (br,
2H). 13C NMR (75 MHz, CDCl3): δ26.04, 27.39, 28.64, 29.03, 29.25,
29.33, 29.47, 29.67, 29.90, 32.76, 33.95, 35.79, 50.85, 78.91, 130.03,
130.49, 155.93. FT-IR (KBr pellet): 3445, 3344, 2977, 2927, 2855,
1692, 1525, 1456, 1390, 1365, 1248, 1174, 1090, 1013, 967, 909, 867,
778, 728, 646, 463 cm−1.
Polymerization of tert-Butyl Henicosa-1,20-dien-11-ylcarbamate
8,8NHBoc (7). 1H NMR (300 MHz, CDCl3): δ 1.21−1.40 (br, m,
28H), 1.41 (s, 9H), 1.91−1.99 (br, 4H), 3.49 (br, 1H), 4.22 (br, d,
1H), 5.29−5.39 (br, 2H). 13C NMR (75 MHz, CDCl3): δ 26.10,
27.44, 28.67, 29.37, 29.70, 29.81, 29.88, 29.98, 32.82, 35.85, 50.93,
78.95, 130.53, 155.93. FT-IR (KBr pellet): 3443, 3344, 2975, 2927,
2854, 1691, 1523, 1456, 1390, 1365, 1247, 1174, 1093, 1019, 967, 914,
864, 778, 724, 645, 464 cm−1.
Polymerization of tert-butyl tricosa-1,22-dien-12-ylcarbamate
9,9NHBoc (8). 1H NMR (300 MHz, CDCl3): δ 1.21−1.41 (br, m,
32H), 1.42 (s, 9H), 2.01 (br, 4H), 3.49 (br, 1H), 4.21 (br, d, 1H),
5.30−5.38 (br, 2H). 13C NMR (75 MHz, CDCl3): δ 26.10, 27.45,
28.67, 29.42, 29.55, 29.74, 29.81, 29.84, 29.90, 30.00, 32.84, 35.84,
50.92, 78.93, 130.10, 130.56, 155.94. FT-IR (KBr pellet): 3445, 3346,
3136, 2975, 2925, 2854, 2248, 1693, 1523, 1456, 1390, 1365, 1247,
1174, 1097, 1048, 1024, 966, 910, 865, 778, 723, 647, 463 cm−1.
Hydrogenation of Unsaturated ADMET Polymers. The crude
polymer solution was transferred to a Parr Bomb glass sleeve and
diluted to ∼200 mL with toluene. Argon was bubbled through the
solution for 30 min, after which a spatula tip of Wilkinson’s catalyst
(RhCl(PPh3)3) was added to the solution and the sleeve was sealed
inside a Parr Bomb equipped with a mechanical stirrer and
temperature control. The vessel was purged three times with 600 psi
hydrogen gas, then filled to 600 psi with hydrogen gas and left for 4
days at room temperature. Upon depressurization, argon was bubbled
through the crude reaction mixture for 30 min. The solution was
concentrated to ∼50 mL and slowly dripped into 1 L of cold
tert-Butyl Undeca-1,10-dien-6-ylcarbamate 3,3NHBoc (1).
1
Monomer is a colorless oil. H NMR (300 MHz, CDCl3): δ 1.20−
1.46 (br, m, 8H), 1.48 (s, 9H), 2.01 (m, 4H), 3.52 (br, 1H), 4.22 (br,
d, 1H), 4.93 (m, 4H), 5.76 (m, 2H). 13C NMR (75 MHz, CDCl3): δ
25.33, 27.60, 28.62, 33.79, 35.25, 50.57, 79.00, 114.78, 138.83, 155.89.
FT-IR (KBr pellet): 3348, 3077, 2978, 2934, 2860, 1814, 1692, 1641,
1522, 1457, 1443, 1416, 1391, 1366, 1284, 1249, 1174, 1120, 1056,
1026, 944, 910, 868, 773, 637 cm−1. ESI/HRMS [2M +1]: calcd for
C16H29NO2, 535.4469; found, 535.4463. Anal. Calcd for CHNO: C,
71.86; H, 10.93; N, 5.24. Found: C, 71.91; H, 11.06; N, 5.23.
tert-Butyl Heptadeca-1,16-dien-9-ylcarbamate 6,6NHBoc (2).
1
Monomer is a waxy white solid that melts at 38 °C. H NMR (300
MHz, CDCl3): δ 1.23−1.40 (br, m, 8H), 1.41 (s, 9H), 2.01 (q, 4H),
3.50 (br, 1H), 4.20 (br, d, 1H), 4.91 (m, 4H), 5.78 (m, 2H). 13C NMR
(75 MHz, CDCl3): δ 26.01, 28.65, 29.05, 29.27, 29.63, 33.97, 35.79,
50.83, 79.00, 114.37, 139.35, 155.92. FT-IR (KBr pellet): 3444, 3346,
3077, 2977, 2928, 2856, 1821, 1703, 1693, 1641, 1522, 1455, 1441,
1415, 1390, 1365, 1248, 1174, 1092, 1057, 993, 909, 869, 778, 750,
725, 636, 555 cm−1. EI/HRMS [2M +1]: calcd for C22H41NO2,
703.6347; found, 703.6327. Anal. Calcd for CHNO: C, 75.16 ; H,
11.75 ; N, 3.98. Found: C, 75.26 ; H, 11.99 ; N, 3.93.
tert-Butyl Henicosa-1,20-dien-11-ylcarbamate 8,8NHBoc (3).
1
Monomer is a waxy white solid that melts at 43 °C. H NMR (300
MHz, CDCl3): δ 1.21−1.41 (br, m, 28H), 1.42 (s, 9H), 2.01 (q, 4H),
3.50 (br, 1H), 4.20 (br, d, 1H), 4.93 (m, 4H), 5.80 (m, 2H). 13C NMR
(75 MHz, CDCl3): δ 26.06, 28.67, 29.14, 29.33, 29.64, 29.76, 29.80,
34.02, 35.82, 50.87, 78.95, 114.31, 139.42, 155.94. FT-IR (KBr pellet):
3348, 3077, 2977, 2926, 2855, 1701, 1641, 1503, 1456, 1390, 1365,
1245, 1173, 1046, 993, 909, 865, 723, 640 cm−1. EI/HRMS [2M +1]:
calcd for C26H49NO2, 815.7599; found, 815.7466. Anal. Calcd for
673
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
methanol. The precipitated polymer was filtered and dried for
characterization.
Polysat3,3NHBoc (9). 1H NMR (300 MHz, CDCl3): δ 1.23 (br,
16H), 1.41 (s, 9H), 3.48 (br, 1H), 4.21 (br, d, 1H). 13C NMR (75
MHz, CDCl3): δ 14.24, 22.82, 25.72, 26.09, 27.89, 28.66, 29.79, 29.91,
32.03, 35.85, 50.90, 78.95, 155.95. FT-IR (KBr pellet): 3446, 3342,
3134, 2928, 2855, 2248, 1692, 1524, 1456, 1390, 1365, 1248, 1175,
1098, 1048, 1020, 909, 865, 802, 733, 667, 647, 556, 463 cm−1.
Polysat6,6NHBoc (10). 1H NMR (300 MHz, CDCl3): δ 1.22 (br,
24H), 1.41 (br, s, 13H), 3.49 (br, 1H), 4.21 (br, d, 1H). 13C NMR (75
MHz, CDCl3): δ 14.33, 22.89, 26.10, 28.67.29.48, 29.86, 29.91, 32.10,
35.84, 50.92, 78.94, 155.95. FT-IR (KBr pellet): 3446, 3346, 3137,
2977, 2924, 2854, 2249, 1695, 1525, 1456, 1390, 1365, 1247, 1175,
1060, 1013, 909, 866, 778, 734, 646, 465 cm−1.
Figure 1. Initial protection strategy for amine monomers: (i) FmocCl,
DMAP, THF; (ii) first-generation Grubbs’ catalyst.
As an alternative protection strategy, the tert-butyl oxy-
carbonyl (Boc) group was employed, because it can be readily
removed using acid or heat. Figure 2 details the synthetic
approach employed to conduct the metathesis polymerization,
hydrogenation, and deprotection. Monomer 1 is a colorless
viscous oil while monomers 2, 3, and 4 are white crystalline
solids that melt at 38, 43, and 46 °C, respectively. As a result, all
four monomers can be polymerized neat in the melt with no
solvent. The ADMET polymerization of the Boc-protected
monomers proceeded normally under vacuum. The molecular
weight and thermal data for the unsaturated polymers are
presented in Table 1. Subsequent hydrogenation was
performed in toluene with Wilkinson’s catalyst under hydrogen
pressure in a Parr reactor. These hydrogenations were done at
room temperature; there was no spectroscopic evidence that
any Boc protection groups were removed during this step.
Structural Analysis with 13C and 1H NMR and IR.
Polysat8,8NHBoc (11). 1H NMR (300 MHz, CDCl3): δ 1.21−1.41
(br, m, 36H), 1.42 (s, 9H), 3.49 (br, 1H), 4.21 (br, d, 1H). 13C NMR
(75 MHz, CDCl3): δ 14.32, 22.88, 26.06, 28.64, 29.83, 29.89, 32.10,
35.80, 50.87, 78.92, 155.93. FT-IR (KBr pellet): 3445, 3348, 3135,
2925, 2854, 2248, 1693, 1526, 1457, 1390, 1365, 1248, 1175, 1096,
1019, 909, 865, 801, 732, 647, 464 cm−1.
Polysat9,9NHBoc (12). 1H NMR (300 MHz, CDCl3): δ 1.15−1.34
(br, 40H), 1.41 (s, 9H), 3.49 (br, 1H), 4.21 (br, d, 1H). 13C NMR (75
MHz, CDCl3): δ 14.33, 22.90, 26.08, 28.66, 29.56, 29.84, 29.94, 32.13,
35.82, 50.88, 78.92, 155.93. FT-IR (KBr pellet): 3446, 3346, 3136,
2925, 2854, 1696, 1523, 1465, 1457, 1390, 1365, 1248, 1175, 1058,
1019, 866, 783, 753, 721, 650, 462 cm−1.
Removal of the Boc Protection Group from the Polymers.
Each saturated, protected polymer was readily dissolved in THF and
transferred to a 10 mL screw-cap vial. The solution was rotovapped
with rapid spinning to create a thin film along the walls of the vials.
The vial was attached to a vacuum vial adapter and placed under high
vacuum (10−3 mmHg) for 1 day to dry. After the polymer was dry, the
vial was submerged in 275 °C sand in an aluminum foil lined heating
mantle and left under heat and vacuum for 2 h. Upon submersion into
the hot sand, each polymer began to slowly melt and then bubble.
Each sample melted and went from a light beige color to a dark brown
color within the first 5 min of heating under vacuum.
1
Primary structural analysis by H- and 13C NMR revealed the
kind of pristine primary structure that can be obtained when
using ADMET polymerizations and hydrogenation reac-
tions.17,25,26 Confirmation of the branch precision and
knowledge of methylene run lengths between branches allows
confident determination of molar ratios of ethylene and vinyl
amine. These proton and carbon spectra are the best
techniques to determine primary structure of monomer,
unsaturated polymer, and saturated polymer.
RESULTS AND DISCUSSION
■
Polymer Design and Synthesis. The preparation of
linear, precisely branched, ethylene-co-vinyl amine (EVAm)
polymers requires the synthesis of a symmetrically branched
α,ω-diene monomer for the ADMET reaction. In light of the
recent successes of other groups performing ROMP on free
amines,13,14 and with the development of more nitrogen
tolerant metathesis catalysts,23 an initial attempt was made to
polymerize the free amine diene. However, the reaction was
unsuccessful due to the tendency of the amine to facilitate
catalyst decomposition. As a result, a protection strategy was
required to polymerize the amine dienes.
The proton spectra in Figure 3 shows the clean and complete
transformation of the 9,9 monomer (4) to unsaturated polymer
(8) and then to the saturated polymer (12). The resonances
from the terminal olefins of 4, at roughly 4.8 and 5.8 ppm,
condense to one peak, at 5.3 ppm in 8, while the chemical shifts
of the other peaks are maintained and slightly broadened. From
the unsaturated (8) to saturated polymer (12), the internal
olefin and its alpha proton peak at 2.0 ppm are completely
removed from the sample through the hydrogenation step. The
hydrogenation of the unsaturated polymer also leads to the
formation of methyl end groups resonating at 0.9 ppm. The
final hydrogenated polymer (12) shows five proton shifts
relating to the polymer: (1) methyl end groups at 0.8 ppm; (2)
backbone protons at 1.23 ppm; (3) nine Boc group protons at
1.41 ppm; (4) proton on the carbon with the amine branch at
3.48 ppm; (5) carbamate nitrogen’s proton at 4.21 ppm.
The same trends are observed in the carbon spectra of the
corresponding 6,6 molecules (2, 6, 10), shown in Figure 4. The
terminal olefin resonances at 130 and 156 ppm in 2 are
condensed to an internal olefin peak in 6, (two peaks due to
cis/trans isomers). This internal olefin peak is then eliminated
from the sample upon hydrogenation.
Use of the 9-fluorenyl carbamate (Fmoc) group as an amine
protection strategy was previously developed in our group by
Leonard et al.24 for the synthesis of amino acid containing
polyolefins. Because of the ease with which the Fmoc group is
removed under mild basic conditions, this same methodology
was attempted for EVAm. The synthesis of the 9,9NHFmoc
monomer was readily accomplished by protecting the
corresponding amine diene with 9-fluorenylmethyl chlorofor-
mate (Fmoc−Cl) to yield a white fluffy powder with a sharp
melting point. However, polymerization of this monomer in
THF led to the formation of dimers and trimers almost
immediately upon addition of catalyst, as observed by the
precipitation of these oligomers from solution (Figure 1).
Attempts to characterize these oligomers failed due to lack of
solubility in any known solvent.
Compound structure and purity was also confirmed with FT-
IR throughout the EVAm copolymer synthesis. The analysis for
all of these copolymers is essentially identical due to the
674
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
Figure 2. Ethylene-co-vinyl amine copolymer synthesis: (i) first-generation Grubbs’ catalyst; (ii) H2 (600 psi), RhCl(PPh3)3, toluene, room
temperature; (iii) 250 °C under vacuum.
Table 1. Molecular Weight and Thermal Data for
Unsaturated Ethylene Vinyl Amine Copolymers:
correspond to the asymmetric and symmetric methylene C−
H stretching motions of the backbone carbons. The carbonyl
stretch of the Boc’s carbamate functionality is observed at 1692
cm−1 with additional carbamyl bands at 1524 and 1248 cm−1.
Scissoring bands from the methylene C−H vibrations are also
readily observed at 1457 cm−1.
Thermal Analysis. Thermal gravimetric analysis (TGA)
and differential scanning calorimetry (DSC) were performed
on each of the three groups of polymer samples: the
unsaturated protected, the saturated protected, and the
saturated deprotected polymers. Table 2 summarizes the
thermal properties exhibited while Figures 5, 6, 7, 10, and 11
show thermograms which detail the decomposition, glass
transition, and melting points of these materials. It is apparent
from this thermal data that the molar ratio of incorporated vinyl
amine has a dramatic effect on the material behavior.
a
b
c
c
c
polymer
mol % vinylamine
Tg (°C)
MW
PDI
Dp
5
6
7
8
22
19.1
−5.4
−8.5
7.4
11.4
14.7
13.3
1.45
1.43
1.99
1.67
21
25
20
20
13
10.5
9.5
−24.2
a
b
Calculated from theoretical repeat unit, confirmed by NMR. 10 °C/
c
min scan rate, values determined from second scan data. Reported in
kg/mol and performed in THF at 40 °C with calibration vs
polystyrene standards.
identical functional groups contained in each material. The
polymerization was verified by the coalescence of two
absorbance bands from α-olefins in monomers at 991 and
908 cm−1 into a single band at 967 cm−1 indicating a mostly
trans 1,2-disubstituted olefin and successful polymerization.27
The elimination of the olefinic band at 967 cm−1 corresponding
to the out-of-plane C−H bend confirms complete hydro-
genation of the ethylene backbone. Strong absorbance bands
present at 2925 and 2854 cm−1 for these copolymers
The decomposition traces of both the unsaturated and
saturated protected amine polymers (Figure 5) are predictable.
Yamamoto28 and Ahn29 have shown in their research that the
Boc group can be removed thermally at about 175 °C.28,29
A
sharp loss in weight occurs at this temperature for each of the
1
Figure 3. Progression of monomer to polymer monitored by H NMR.
675
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
Figure 4. Progression of monomer to polymer monitored by 13C NMR.
losses correspond to the Boc protection group being cleaved
from the amine releasing carbon dioxide and isobutene from
each repeat unit. The calculated predictive weight loses of 42,
31, 26, and 25% are in excellent agreement with these
experimental values. The TGA traces for both the unsaturated
and saturated polymer families are nearly identical which prove
that the addition of hydrogen to the internal alkene has a
minimal net effect on the weight loss. It can be determined
from these weight loss profiles that the thermally deprotected
polymer is stable and exists over a 100° range, indicating that
these materials are excellent candidates for a single thermal
deprotection step.
Table 2. Thermal Data for the Protected and Deprotected
Polymers
a
b
b
polymer
mol % vinylamine
Tg (°C)
Tm (°C)
9
22
4
2
N/A
N/A
N/A
N/A
N/A
49
10
11
12
13
14
16
13
10.5
9.5
22
−8
2
10
13
N/A
N/A
9.5
44
a
b
Calculated from theoretical repeat unit, confirmed by NMR. 10 °C/
min scan rate, values determined from second scan data.
Figure 6 shows the DSC data (second heating scan) for the
series of unsaturated and saturated protected polymers. All four
unsaturated polymers are amorphous, but the Tg’s are
consistent with ADMET sequenced materials.27 Amorphous
sequenced copolymers occur as a consequence of steric
congestion along the polymer backbone, thus preventing the
ethylene run lengths between branches to crystallize. The
eight protected polymers; the shoulder or plateau area of each
curve represents the stable deprotected amine polymer. The
percent weight losses experimentally observed in these
decomposition curves were 45, 32, 29, and 25% as measured
to the inflection point of the plateau. These percent weight
Figure 5. TGA traces for (left) unsaturated protected polymers (right) saturated protected polymers.
676
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
Figure 6. DSC of ADMET (left) unsaturated protected polymers (right) saturated protected polymers.
Figure 7. TGA traces of (left) polysat6,6NHBoc (10) and polysat6,6NH2 (14) (right) polysat9,9NHBoc (12), and polysat9,9NH2 (16) polymers.
1
Figure 8. H NMR of (top) polysat6,6NH2 (14) and (bottom) polysat6,6NHBoc (10).
tert-butyl carbamate protection group explains the general trend
of a decreasing Tg with decreasing branch frequency, since it
allows for hydrogen bonding with other such protecting groups.
This hydrogen bonding allows branches to become associated
with each other to form a physically cross-linked structure. As
the number of H-bond cross-links decreases in the compounds
5, 6, 7, and 8, the polymer chain has greater flexibility and a
lower Tg. The DSC traces for the saturated protected polymers
each shows a complicated transition, which resembles the start
of a Tg but then appears to lead directly into a melt. The
general trend observed in precision polymers previously
synthesized in this group demonstrates that increasing the
pendant branch frequency yields materials with less and less
crystalline character, until a critical threshold is met and the
material becomes amorphous.15,25,26 This threshold is not
obvious in the present data, because the polymer with the
677
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
Figure 9. 15N CP/MAS spectra of (a) protected precision polymer POLY-NHBoc, and (b) deprotected precision polymer POLY66-NH2.
frequent branches is needed to determine if the trend holds for
precision PEVAm.
Deprotection Strategy. Initial attempts to deprotect
these polymers were carried out in solution with hydrochloric
acid. The protected polymer was readily dissolved in a
minimum amount of a 1:1 THF/dioxane solvent mixture,
and 10 vol equiv of 4 M HCl in dioxane were added at room
temperature. Within minutes, a dark brown polymer started to
precipitate onto the sides of the round-bottom flask. After 1 h
the solution was extracted with ether, but no polymer was
obtained upon rotary evaporation of the organic layer. Multiple
attempts to remove the polymer remaining on the walls of the
flask were unsuccessful due to lack of solubility. The polymer
was finally removed from the flask by physically scraping it
from the sides, placing the dark brown scrapings into a vial, and
drying them.
Figure 10. TGA traces of polysat9,9NH2 polymers deprotected from
heat and acid.
It is believed that the negligibly soluble polymer on the flask
walls was the ammonium chloride salt of the amine. Upon
protic acid deprotection in solution, the corresponding
ammonium salt branches are attracted to each other and likely
cluster together tightly with the polymer backbone coil around
them, thus preventing any further solvation of the material.
In order to prevent this strong ionic aggregation, the thermal
degradation information gathered from the TGA thermograms
shown in Figure 5 was advantageously used. To employ this
deprotection technique, the polymer was cast as a thin film in a
10 mL vial and placed in a 275 °C sand bath under vacuum. For
each of these materials, the protected, tan-colored polymer
films turned dark brown within minutes upon heating with
bubbles, presumed to be carbon dioxide and isobutene,
eliminated from the viscous melted polymer. Since this
deprotection is performed under vacuum, the isobutene is
removed upon elimination with no further need of purification.
Figure 7 shows the overlapping TGA traces of the saturated
protected 6,6 polymer and 9,9 polymer with their respective
deprotected counterparts. The weight loss corresponding to the
Boc group no longer exists in the TGA trace from the polymer
recovered from the vial. These thermally deprotected polymers,
Figure 11. DSC of the deprotected amine branch every 9th, 15th, and
21st carbon on polymer.
most closely spaced pendant groups (every ninth carbon, 9)
exhibits a melt peak. Additional work on polymers with more
678
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
like the chemically deprotected ones, have negligible solubility
in all solvents tested. However, a small amount of the
deprotected 6,6 saturated polymer dissolved in CDCl3, and
the corresponding 1H NMR spectra are shown in Figure 8. No
13C NMR spectra was observed due to this lack of copolymer
solubility.
To better elucidate both the protected and deprotected 6,6
amine polymer’s chemical structures and demonstrate the
success of synthesis, natural-abundance 15N solid state NMR
(SS-NMR) spectra were collected at Max Planck Institute for
Polymer Research in Mainz, Germany. The SS-NMR spectros-
copy when coupled with cross-polarization magic angle
spinning (CP-MAS) provides excellent sensitivity and narrow
line widths. Moreover, this technology also eliminates possible
errors arising from the partial solubility of the deprotected
precision amine polymer samples.
copolymers. This is contrary to the trend observed in the
series of precision ethylene copolymers prepared in our
laboratory, in which the melting points usually increase as the
number of CH2 groups between branches increases.26 In
previous polymer families made in our group,25 the polymer
substituted on every ninth carbon is amorphous. This trend is
upheld for the PEVAm materials, Figure 11, as the polymer
with an amine branch on every ninth carbon appears
completely amorphous. Unfortunately, a lack of copolymer
with an amine on every 19th carbon prevented thermal analysis
for this material.
CONCLUSIONS
■
Reported for the first time, a family of four sequenced
copolymers of ethylene with vinyl amine has been prepared
with predetermined comonomer ratios. Although metathesis
catalysts are evolving to become more tolerant of amine and
nitrogen functionality, the amine functionalized dienes
synthesized here must be protected prior to ADMET
polymerization. The Boc protected monomers provided soluble
polymers while the Fmoc protected analogues did not. These
polymers possess exact ethylene run lengths between pendant
primary amine branches on every 9th, 15th, 19th, or 21st
carbon along the backbone. Spectroscopic analysis via NMR
and FT-IR affirms the microstructural control achieved via
metathesis polymerization. The pristine nature of these
copolymers’ primary structures imparts marked effects on
thermal behavior. Mass losses observed by TGA verify that the
thermal deprotection reactions yielded the expected amine
copolymers. Both thermal and chemical deprotection ap-
proaches yielded minimally soluble product but the thermal
approach provided less contamination to the sample. Although
this poor solubility of the deprotected PEVAm polymer
hampered characterization efforts, a combination of 15N solid-
state NMR, 1H NMR, and TGA confirmed quantitative
deprotection. The polymers with an amine branch on every
15th and 21st carbon were shown to be crystalline, whereas the
polymer with an amine on every ninth carbon is amorphous.
Compared to commonly seen 13C SS-NMR, 15N CP-MAS
NMR offers generally simple and readily interpretable 15N
spectra in terms of probing a polymer’s structure. Figure 9
shows the spectra of both a protected and deprotected ADMET
amine polymer: POLY66-NH2 (14) and POLY66-NHBoc
(10), each of which exhibits a single resonance at −344.51 ppm
and −285.74 ppm, respectively. The signal at −344.51 ppm in
Figure 9b falls within the resonance range of primary amine
NH2 groups30−32 and can be readily assigned to the amine
groups on the deprotected POLY66-NH2 (14) side chains.
Considering the single peak at −285.74 ppm from the
protected sample as shown in Figure 9a, this peak should be
the only nitrogen resonance arising from the amide groups in
POLY66-NHBoc (10), if the deprotection step is successful,
which is indeed the case herein. It is known that amide
isotropic chemical shifts are highly sensitive to both hydrogen
bonds and protonation at the carbonyl oxygen.33 The single
resonance at −285.74 ppm in Figure 9a is quite close to the
reported 15N isotropic chemical shifts from amides and
urethanes.34−36 The introduction of the electron-withdrawing
Boc group causes the nitrogen nuclei in POLY66-NHBoc (10)
to shift downfield exhibiting a significantly more positive
chemical shift.
In short, 15N solid-state NMR analysis has demonstrated that
the deprotection step is successful based on the significant
isotropic chemical shift changes between the protected and
deprotected precision polymers. The synthetic route employed
in this study is applicable to offer precise amine polymers.
Figure 10 contains the TGA traces of both the saturated 9,9
polymer (16) deprotected by heat and (16) deprotected by
acid. These overlapping thermograms demonstrate the biggest
advantages of thermal over acid deprotectionsolvent and
counterion contamination. The weight loss on the acid
deprotected polymer begins below 100 °C, and this weight
loss continues until the main chain decomposes at 400 °C.
However, the thermally deprotected polymer shows no solvent
contamination or other impurity associated weight loss upon
TGA analysis and is immediately ready for further analysis.
The final deprotected polymers with amine groups on every
15th, and 21st carbon polymers exhibit crystallinity. The DSC
traces in Figure 11 show that the polymer with an amine on
every 15th carbon (14) has a sharp melt at 49 °C, whereas 16
(an amine on every 21st carbon) has a broader melt at 44 °C.
Although the every 15th polymer exhibits a sharper melting
point than the 21st material, we believe the hydrogen bonding
of the branches may induce different chain packing and alter
the crystallinity of this material relative to the other
AUTHOR INFORMATION
Corresponding Author
*E-mail: wagener@chem.ufl.edu.
■
ACKNOWLEDGMENTS
■
The authors would like to thank the National Science
Foundation (Grant No. DMR-0703261) for funding. Addi-
tional thanks is owed to Dr. Robert Graf and Professor Hans
Spiess of the Max Planck Institute for Polymer Research in
Mainz, Germany, for use of their Solid-State NMR
instrumentation. Generous support from the Army Research
Office and Materia Inc. for the development and acquisition of
catalysts is also acknowledged.
REFERENCES
■
(1) Robeson, L. M.; Kuphal, J. A.; Vratsanos, M. S. J. Appl. Polym. Sci.
1996, 61, 1561−1569.
(2) Kobayashi, S.; Hiroishi, K.; Tokunoh, M.; Saegusa, T.
Macromolecules 1987, 20, 1496−1500.
(3) Kobayashi, S.; Suh, K. D.; Shirokura, Y. Macromolecules 1989, 22,
2363−2366.
(4) Martel, B.; Pollet, A.; Morcellet, M. Macromolecules 1994, 27,
5258−5262.
(5) Noro, K. Polyvinyl Alcohol 1973, 91−120.
679
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680

Macromolecules
Article
(6) Jones, G. D.; Zomlefer, J.; Hawkins, K. J. Org. Chem. 1944, 9,
500−512.
(7) Maki, Y.; Mori, H.; Endo, T. Macromol. Chem. Phys. 2007, 208,
2589−2599.
(8) Reynolds, D. D.; Kenyon, W. O. J. Am. Chem. Soc. 1947, 69,
911−915.
(9) Fischer, T.; Heitz, W. Macromol. Chem. Phys. 1994, 195, 679−
687.
(10) Madl, A.; Spange, S. Macromol. Symp. 2000, 161, 149−157.
(11) Witek, E.; Pazdro, M.; Bortel, E. J. Macromol. Sci., Part A: Pure
Appl. Chem. 2007, 44, 503−507.
(12) Wingard, R. E.; Larson, E. R. U.S. Patent 4,255,548, March 10,
1980.
(13) Breitenkamp, R. B.; Ou, Z.; Breitenkamp, K.; Muthukumar, M.;
Emrick, T. Macromolecules 2007, 40, 7617−7624.
(14) Sutthasupa, S. S., F.; Masuda, T. Macromolecules 2009, 42,
1519−1525.
(15) Baughman, T. W.; Chan, C. D.; Winey, K. I.; Wagener, K. B.
Macromolecules 2007, 40, 6564−6571.
(16) Baughman, T. W.; van der Aa, E.; Wagener, K. B.
Macromolecules 2006, 39, 7015−7021.
(17) Boz, E.; Wagener, K. B.; Ghosal, A.; Fu, R. Q.; Alamo, R. G.
Macromolecules 2006, 39, 4437−4447.
(18) Gomez, F. J.; Wagener, K. B. J. Organomet. Chem. 1999, 592,
271−277.
(19) Hopkins, T. E.; Pawlow, J. H.; Koren, D. L.; Deters, K. S.;
Solivan, S. M.; Davis, J. A.; Gomez, F. J.; Wagener, K. B.
Macromolecules 2001, 34, 7920−7922.
(20) Hopkins, T. E.; Wagener, K. B. Macromolecules 2003, 36, 2206−
2214.
(21) Watson, M. D.; Wagener, K. B. Macromolecules 2000, 33, 8963−
8970.
(22) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999,
1, 953−956.
(23) Vieira, E. M.; Snapper, M. L.; Hoveyda, A. H. J. Am. Chem. Soc.
2011, 133.
(24) Leonard, J. K.; Hopkins, T. E.; Chaffin, K.; Wagener, K. B.
Macromolecular Chemistry And Physics 2008, 209, 1485−1494.
(25) Baughman, T. W.; Sworen, J. C.; Wagener, K. B. Macromolecules
2006, 39, 5028−5036.
(26) Sworen, J. C.; Smith, J. A.; Berg, J. M.; Wagener, K. B. J. Am.
Chem. Soc. 2004, 126, 11238−11246.
(27) Baughman, T. W.; Wagener, K. B. Recent Advances in ADMET
Polymerization; Springer Verlag: Berlin and Heidelberg, Germany,
2005.
(28) Yamamoto, T.; Yoshizawa, M.; Mahmut, A.; Abe, M.; Kuroda,
S.; Imase, T.; Sasaki, S. J. Polym. Sci., Part A: Polym. Chem. 2005, 43,
6223−6232.
(29) Ahn, K. D.; Lee, Y. H.; Koo, D. I. Polymer 1992, 33, 4851−4856.
(30) Bottot, R. E.; Coxon, B. J. Am. Chem. Soc. 1983, 105, 1021−
1028.
(31) Rao, Y.; Kemp, T. F.; Trudeau, M.; Smith, M. E.; Antonelli, D.
M. J. Am. Chem. Soc. 2008, 130, 15726−15731.
(32) Schwab, M. G.; Fassbender, B.; Spiess, H. W.; Thomas, A.;
Feng, X.; Mullen, K. J. Am. Chem. Soc. 2009, 131, 7216−7217.
(33) Andreis, M.; Koenig, J. L. Adv. Polym. Sci. 1995, 124, 192−237.
(34) Duff, D. W.; Maciel, G. E. Macromolecules 1990, 23, 4367−4371.
(35) Facelli, J. C.; Purmire, R. J.; Grant, D. M. J. Am. Chem. Soc.
1996, 118, 5488−5489.
(36) Levy, G. C.; Lichter, R. L. Nitrogen-15 Nuclear Magnetic
Resonance Spectroscopy; J. Wiley: New York, 1979.
680
dx.doi.org/10.1021/ma202233a | Macromolecules 2012, 45, 671−680