Aqueous poly(arylacetylene) dispersions

Article abstract of DOI:10.1021/ma1013572

Aqueous poly(phenylacetylene) dispersions were obtained by catalytic polymerization in emulsion with a phosphine-modified Pd(II) catalyst. A range of mono- and bidentate phosphines were screened. A tBu₂P(CH ₂)₃PtBu₂

Full text of DOI:10.1021/ma1013572

8718 Macromolecules 2010, 43, 8718–8723
DOI: 10.1021/ma1013572
Aqueous Poly(arylacetylene) Dispersions
Johannes Huber and Stefan Mecking*
Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz,
€
Universitatsstrasse 10, D-78457 Konstanz, Germany
Received June 18, 2010; Revised Manuscript Received September 6, 2010
ABSTRACT: Aqueous poly(phenylacetylene) dispersions were obtainedby catalytic polymerizationinemulsion
with a phosphine-modified Pd(II) catalyst. A range of mono- and bidentate phosphines were screened.
A tBu2P(CH2)3PtBu2-modified catalyst exhibits very high rates up to 2ꢀ105 TO h-1 (TO=moles of monomer
converted per mole of metal present in the reaction mixture) in the preparation of colloidally stable poly-
(phenylacetylene) dispersions. Polymerization in miniemulsion afforded dispersions with up to 36 wt % solids
content and average particle sizes of ca. 130 nm. From microemulsions dispersions with ca. 25 nm particle size
were obtained.
Introduction
relatively large given the large amount of surfactant employed,
which exceeds the amount of monomer. The polymers formed have
Polymer dispersions have been studied intensely from a funda-
mental as well as applications oriented perspective.1,2 Thus, aqueous
polymer dispersions are applied on a large scale in environmentally
benign coatings and paints. By comparison to processing from
solution in organic solvents, polymer dispersions can be beneficial
for sensitive substrates and for the generation of nanocomposites.1,3
Moreover, otherwise unprocessable insoluble and intractable poly-
mers can be processed from dispersions.4 Polymer dispersions are
prepared most often by free-radical emulsion polymerization in
a nonsolvent for the polymer, usually water.5,6 In recent years, con-
trolled and nonradical polymerization routes to aqueous polymer
dispersions have found increased interest.7-13 Coordination poly-
merizations in emulsion can offer access to nanoparticles of
polymers with microstructures inaccessible by other polymeriza-
tion mechanisms.14 Also, in terms of the monomers polymeri-
zable, coordination polymerization is largely complementary to
free-radical polymerization.
The preparation and properties of substituted polyacetylenes
have received considerable attention.15,16 Their molecular struc-
ture and physical properties, which comprise e.g. luminescence
and liquid crystallinity, are influenced by the rigidity of the poly-
acetylene backbone which again is altered by the side-chain
subsitutents.17 This is reflected in the polymer chain structure,
e.g., in helicality.
molecular weights around Mn 2 ꢀ 104 g mol-1, with narrow
distributions, as determined by GPC in THF vs polystyrene
standards.20 Metathesis cyclopolymerization of 1,6-heptadiynes,
HCCCH2C(CO2R)2CH2CCH, with ruthenium alkylidenes bound
to specific block copolymers has been reported to afford aqueous
dispersions of the resulting polymers with productivities of 102 TO.21
Because of the polymerization mechanism, by contrast to acyclic
polymers from insertion polymerization of monofunctional sub-
stituted acetylenes, in these polymers every other back-
bone double bond is a member of a five-ring.
Cationic palladium complexes are well-known to copolymerize
olefins with carbon monoxide by an insertion mechansim,22 also
in aqueous systems,23 and they have been noted to polymerize
substituted acetylenes in nonaqueous systems.24 On the other hand,
mechanistic studies of acetylene insertion in cationic palladium
complexes with bidentate nitrogen ligands [(N∧N)Pd(CH3)(L)]þ
revealed that after insertion of three acetylene molecules stable,
unreactive π-allyl complexes were formed.25
We now give a first full account on the preparation of poly-
(arylacetylene) dispersions by polymerization in emulsion, utiliz-
ing very active phosphine-modified Pd(II) catalysts.26
Results and Discussion
Acetylene and substituted acetylenes can be polymerized by
insertion polymerization or by metathesis polymerization.15,16
The water sensitivity of common catalysts based on titanium
(insertion) and tungsten (metathesis) prohibits their use in aque-
ous systems. Insertion polymerization of substituted acetylenes
in biphasic aqueous systems has been reported, most prominently
with Rh catalysts. Catalyst productivities were moderate, with
typically 103 TO (TO = turnover, moles of substrate converted
per mole of metal present in the reaction mixture).18,19 Polymer-
ization of alkylacetylenes substituted with chiral substituents in
aqueous surfactant solution containing dimethylformamide and
SDS surfactant by a hydrophobic rhodium catalyst yielded
dispersions of helical, optically active polymers. Productivities
were limited, and a ratio of monomer:Rh of 50 was employed.
Average particle sizes observed by TEM of 70-100 nm are
Catalyst Screening. A range of mono- and bidentate phos-
phines varying in chelate ring size, steric bulk at the phos-
phorus atoms, and their electronic properties were screened
for their ability to form an active Pd(II) catalyst for phenyl-
acetylene polymerization (Tables 1 and 2). These studies
were carried out in single phase homogeneous methanol
solutions. By comparison to multiphase aqueous systems,
this reduces the number of parameters potentially influenc-
ing the experiments such as droplet sizes, the surfactant
concentration, or emulsion preparation procedure. In-situ
catalyst systems Pd(OAc)2/phosphine/methanesulfonic acid
were employed.22 Concerning the formation of the active species,
mechanistic studies on carbonylation reactions with such
catalysts suggest that the role of the acid is protonation of the
acetate ligands to acetic acid to generate a weakly coordinated
species (P∧P)Pd2þ 22
. Such species can react with methanol to
*Corresponding author. E-mail: stefan.mecking@uni-konstanz.de.
afford a metal hydride,27 which promotes polymerization.
pubs.acs.org/Macromolecules
Published on Web 10/08/2010
r 2010 American Chemical Society

Article
Macromolecules, Vol. 43, No. 21, 2010 8719
Table 1. Phenylacetylene Polymerization with Monophosphine-
bulk from the corresponding C3-bridged n-hexyl- and cyclo-
hexyl-substituted diphosphines utilized in this work (entries
2-7 and 2-8), cone angles of 114° and 142°, respectively, have
been determined. The extreme steric bulk of the tert-butyl
group is demonstrated by a cone angle of 182° for PtBu3 vs
145° for PPh3 and 170° for PCy3.28 From the comparison of
the polymerization results with trialkyl-substituted diphos-
phines R2P(CH2)3PR2 (R=n-hexyl, Cy, tBu) it appears that
a high steric bulk of R is decisive for catalyst performance.
Diphosphines tBu2P-X-PtBu2 (X=-(CH2)3-,-(CH2)4-,
-CH2(o-C6H4)CH2-) do not differ substantially in the steric
bulk or electronic properties of the phosphorus donors, but in
the chelate ring size formed upon bidentate, chelating coordi-
nation to a metal center. The phosphane with the propan-
1,3-diyl backbone should form more stable six-membered
chelate complexes vs seven-membered chelates with the
butan-1,4-diyl backbone. The large difference in catalytic
properties observed with these two diphosphines suggests
that a chelating bidentate coordination mode indeed occurs
during catalysis. This is in agreement with the high catalyst
activity also observed for the o-xylene-R,R0-diyl backbone
which should afford a seven-membered, but relatively stable,
chelate due to the stiff backbone and spacial arrangement of
the P donors.
Modified Catalystsa
phosphorus/
palladiumb
conversion/
yield (%)
entry
1-1
phosphine
TONc
HPtBu2
6:1
2:1
1:1
6:1
2:1
6:1
1:1
6:1
2:1
1:1
6:1
2:1
1:1
6:1
2:1
1:1
0
2
1
0
1
3
3
3
3
1
0
7
1
0
1
1
0
15
13
2
10
29
26
27
30
10
0
63
7
4
5
10
1-2
1-3
1-4
MePtBu2
PnBu3
PnOct3
1-5
1-6
PPh3
PCy3
a Polymerization at 25°C overnight. 50 μmol of Pd(OAc)2, 1 drop of
methanesulfonic acid, 5.0 mL of phenylacetylene (46 mmol) in 25 mL of
methanol. b Molar ratio. c TON = turnover number = moles of reacted
monomer per mole of Pd.
Table 2. Phenylacetylene Polymerization with Diphosphine-Modified
Catalystsa
Polymerization of phenylacetylene in the presence of 4 vol
% of water under conditions otherwise identical to entry 2-1
also resulted in complete monomer conversion, indicating
that the catalyst is not particularly sensitive toward water.
An excess of phosphine ligand (P:Pd = 6:1) reduces cata-
lyst activity in all cases except for the tert-butyl-substituted
phosphines. Phosphines coordinate relatively strongly and in
excess will block coordination sites for the substrates. The
different behavior of the tert-butyl-substituted phosphines
observed may be due to coordination being hindered to a
certain extent by the very bulky substitution of the phos-
phorus donors. Competitive protonation of the electron-rich
phosphine by the acidic catalyst component may also play
a role.29
Poly(phenylacetylene) Dispersions. A high degree of dis-
persion of the reaction mixture is a prerequisite for the prep-
aration of submicrometer particle dispersions. In the case of
catalytic polymerization with lipophilic catalyst precursors,
this can be achieved by dispersing the catalyst precursor
as a solution in the organic phase of an aqueous mini- or
microemulsion.30 The organic phase can be a small amount
of added organic solvent, e.g., toluene, or in reactions of
monomers which are liquid under reaction conditions also
the neat monomer. In the latter case, care must be taken that
the polymerization only starts after the emulsification pro-
cedure. Otherwise, large colloidally unstable particles will
form. A mixture of an aqueous SDS solution with a solution
of Pd(OAc)2 and tBu2P(CH2)3PtBu2 in phenylacetylene was
ultrasonicated to form a miniemulsion. Subsequent addition
of a drop of methanesulfonic acid triggered the polymeriza-
tion, as evidenced by a color change of the emulsion to deep
yellow, and the onset of heat evolution in experiments with
higher monomer volumes and catalyst loadings (Table 3).
Yellow poly(phenylacetylene) dispersions, with a slight
orange touch at higher solids contents, are formed. Even
at a low catalyst loading of 0.4 μmol (entry 3-6) complete
monomer conversion was observed. This corresponds to a
productivity of 2ꢀ105 TO in a 1 h polymerization experiment.
Polymer molecular weights are chain transfer controlled
(entries 3-2 to 3-6). Dispersions of up to 36 wt % polymer
solids content were prepared. Volume average particle sizes
are 110-160 nm, as determined by DLS, depending on the
monomer volume portion. The dispersions are colloidally
phosphorus/ conversion/
palladiumb yield (%) TONc
entry
diphosphine
2-1 tBu2P(CH2)3PtBu2
2-2 tBu2P(CH2)4PtBu2
2-3 H2P(CH2)3PH2
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
6:1
2:1
100
100
7
4
0
0
0
3
0
1
0
1
0
0
0
1
96
49
916d
909d
65
32
0
0
0
23
0
7
0
12
0
0
2
12
877d
449
2-4 Ph2PCH2PPh2
2-5 Ph2P(CH2)2PPh2
2-6 Ph2P(CH2)3PPh2
2-7 nHex2P(CH2)3PnHex 2
2-8 Cy2P(CH2)3PCy2
2-9 tBu2PCH2(o-C6H4)CH2PtBu2
a Polymerization at 25 °C overnight. 50 μmol of Pd(OAc)2, 1 drop of
methanesulfonic acid, 5.0 mL of phenylacetylene (46 mmol) in 25 mL of
methanol. b Molar ratio. c TON = turnover number = moles of reacted
monomer per mole of Pd. d Limited by quantitative conversion.
A number of monophosphines were found to afford active
catalysts of phenylacetylene, albeit these display moderate
rates only (Table 1).
More active catalysts were obtained with appropriate
diphosphines (Table 2). Various diphosphines with diaryl-
alkyl or trialkyl substitution of the phosphorus donor with
primary or secondary alkyl groups afforded catalysts with
very low activities at the most (entries 2-3 to 2-8). Only
diphosphines substituted with tert-butyl groups afforded
very active catalysts for phenylacetylene polymerization
(entries 2-1, 2-2, and 2-9). This is in agreement with Drent
and Pello’s previous notation that the catalyst system with
tBu2P(CH2)3PtBu2 as a phosphine ligand is highly active for
polymerization of acetylenes.24a
The steric bulk of phosphane ligands can be described by
Tolman’s cone angle. The Tolman cone angles for Ph2P-
(CH2)nPPh2 (n=1-3; entries 4-6 in Table 2) are 121°, 125°,
and 127°, respectively. For Et2P(CH2)2PEt2 and Cy2P-
(CH2)2PCy2, which should not differ substantially in steric

8720 Macromolecules, Vol. 43, No. 21, 2010
Huber and Mecking
stable for more than a year, as evidenced by no significant
change in particle size occurring. TEM images demonstrate
the poly(phenylacetylene) particles to be spherical (Figure 1).
The polymerization of 3-methoxy-4-n-hexyloxyphenyl-
acetylene (MHPA), 1-naphtylacetylene (NA), and 9-anthra-
cenylacetylene (AA) was studied (Table 4). Polymerizations
were carried out at 60 °C. At this temperature all monomers
are liquid. The reactivity of the catalyst system employed
toward these monomers appears to be lower by comparison
to phenylacetylene (PA). While the latter was converted
completely at a catalyst loading of 0.2 μmol under the
conditions studied (entry 4-1), MHPA and NA were only
converted to about 15%. However, complete conversion of
these monomers was achieved at a catalyst loading of 2 μmol,
corresponding to a catalyst productivity of 5.4 ꢀ 103 TO
(MHPA) and 8.2 ꢀ 104 TO (NA). Whereas the particle size
distribution of poly(phenylacetylene) dispersions was mono-
modal (131 nm volume average size), the particle size dis-
tributions of the poly-MHPA and poly-NA dispersions were
bimodal, as determined by the DLS method employed, when
undiluted monomers were used (entries 4-2 to 4-5). This is
due to the higher viscosity of the monomers MHPA and NA,
which hampers the generation of uniform small droplets in
the miniemulsification step, as concluded from polymeriza-
tions of emulsions of MHPA and NA monomers diluted with
hexane, which resulted in monomodal dispersions (entries
4-7 and 4-8). For the poly-MHPA from entry 4-3, a molecular
weight of Mw = 1.2 ꢀ 105 (Mw/Mn 3.6) was determined.31
Microemulsions represent very highly disperse biphasic
systems. Free-radical polymerization in microemulsions32
and also catalytic polymerizations33 can afford polymer parti-
cles with sizes as low as 5-10 nm. A microemulsion is a
thermodynamically stable mixture of at least two immiscible
liquids and a surfactant, which exists in a certain range
of compositions. Frequently, an alcohol is added to achieve
the microemulsion regime. Microemulsions can possess
globular phase structures (oil-in-water, o/w, or water-in oil,
w/o) as well as lamellar or irregular bicontinuous structures.32
Spontaneous formation is an indicator for the existence of a
microemulsion.
For the system studied, a suitable composition which is in
the microemulsion regime was found to be phenylacetylene:
SDS:pentanol:water in a mass ratio of 6:8:4:82. Gentle stirring
overnight afforded a transparent microemulsion. Other
than miniemulsions, microemulsions are highly dynamic. In
order to prevent premature polymerization, the catalyst and
monomer must be microemulsified separately. After mixing
of the two microemulsions, the oil phases containing the
catalyst solution and the monomer can exchange by contin-
uous merging and separation. The equilibrated monomer
and catalyst microemulsions were mixed, and polymeriza-
tion was started by addition of methanesulfonic acid. Even at
a low catalyst loading of 0.4 μmol complete monomer con-
version was observed, corresponding to a catalyst productivity
of 7ꢀ104 TO in a 1 h experiment. Transparent yellow dispersions
with solids contents of ∼6% were formed (Table 5). Note
that the solids content is limited by the necessity of the initial
reaction mixture being in the microemulsion regime. Volume
average particle sizes of 25-29 nm were determined by DLS
(Figure 2 and Table 5). Particle sizes are largely independent
of the catalyst concentration. TEM analysis of the particles
(Figure 3) is in agreement with the DLS studies.
Table 3. Polymerization of Phenylacetylene in Monomer
Miniemulsionsa
n(Pd) polymer solids particle
molecular
Mwc/
entry (μmol) content (%) sizeb (nm) PDI weightc (Mw) Mn
3-1
3-2
3-3
3-4
3-5
3-6
30
20
4.0
2.0
1.0
0.4
36
20
19
18
17
17
142
160
137
117
114
112
0.18
0.13
0.12
0.12
0.14
0.18
4.2 ꢀ 104
3.5 ꢀ 104
3.9 ꢀ 104
3.5 ꢀ 104
3.1 ꢀ 104
4.2
3.8
4.3
4.3
4.6
a Polymerization at room temperature, 1 h polymerization time.
Pd(OAc)2/t-Bu2P(CH2)3P-t-Bu2 1:3 molar ratio. Total volume of reaction
mixture: 50 mL; ca. 9 g of phenylacetylene (entry 3-1: 18 g); 1% aque-
ous SDS solution. b Volume average particle size determined by DLS.
cMolecular weights determined by GPC in THF vs linear polystyrene
standards.
As in the polymerization in miniemulsions, molecular
weights are controlled by chain transfer (entries 5-1 to 5-5).
“Doped” bulk polyacetylene possesses electrical conduc-
Figure 1. TEM image of poly(phenylacetylene) particles from poly-
merization in miniemulsion (entry 3-4; number-average diameter deter-
mined: 57 nm).
tivities of 102-105 S cm-1 34
By comparison to the parent
.
Table 4. Polymerization Results of Various Arylacetylenes in Aqueous Emulsiona
entry
monomer
catalyst (μmol)
polymer solids content
particle sizeb
monomer conversion
color of the latex
4-1
4-2
4-3
4-4
4-5
4-6
4-7d
4-8e
PA
0.2
0.2
2.0
0.2
2.0
2.0
2.0
2.0
16.5%
2.4%
16.4%
2.2%
16.4%
(coagulated)
3.0%
131 nm
quantitative
15%
yellow
yellow
yellow
dark violet
dark violet
dark brown
dark violet
yellow
MHPA
MHPA
NA
NA
AA
100/654 nm
217 nm/1.1 μm
122 nm/1.0 μm
61 nm/1.1 μm
615 nm/84 nm
36 nm
quantitative
13%
quantitative
c
-
NA
MHPA
quantitative
quantitative
6.6%
119 nm
a Polymerization temperature 60 °C; reaction time 1 h; Pd(OAc)2/t-Bu2P(CH2)3P-t-Bu2 = 1:3; total volume: 15 mL; 2.5 g of monomer, 150 mg of SDS;
10 min ultrasonication. b Volume average particle size determined by DLS; bimodal distributions determined with the method employed for samples 4-2
to 4-5. c Coagulated during polymerization, conversion could not be determined due to inclusion of monomer into the insoluble polymer. d 0.5 g of
monomer in 2.5 g of hexane. e 1.0 g monomer in 2 g of hexane.

Article
Macromolecules, Vol. 43, No. 21, 2010 8721
Table 5. Polymerizations of Phenylacetylene in Aqueous Monomer
Microemulsionsa
in aqueous emulsions. Catalyst productivities of 2 ꢀ 105 mol turn-
overs were observed. Colloidally stable poly(phenylacetylene)
dispersions with polymer solids contents of up to 36 wt % were
obtained. With a microemulsion technique very small particles
of <30 nm size are accessible. Substituted phenylacetylenes were
also amenable to polymerization to afford stable dispersions with
substantial solids contents.
n(Pd) polymer solids particle sizeb
molecular
c
entry (μmol) content (%)
(nm)
weightc (Mw) Mw/Mn
5-1
5-2
5-3
5-4
5-5
10
5
2.5
1.25
0.4
5.9
6.0
6.2
6.0
5.6
25
27
27
29
29
5.5 ꢀ 103
3.4 ꢀ 104
3.7 ꢀ 104
2.6 ꢀ 104
3.4 ꢀ 104
2.7
5.1
4.5
5.7
5.3
Experimental Section
a Polymerization temperature 25 °C; reaction time 1 h; Pd(OAc)2/
t-Bu2P(CH2)3P-t-Bu2 = 1:3; total volume: 50 mL; 6.0 wt % phenylacetylene,
8.0 wt % SDS, 4.0 wt % pentanol. b Volume average particle size determined
by DLS. c Determined by GPC in THF vs linear polystyrene standards.
General Methods and Materials. All manipulations involving
phosphines were carried out under an inert atmosphere in a
drybox or by standard Schlenk techniques. THF was distilled
from sodium. Demineralized water was degassed by distillation
under argon. NMR spectra were recorded on a Varian Unity
INOVA 400 or on a Bruker AC 250 spectrometer. 1H and 13
C
NMR chemical shifts were referred to the solvent signal. Size
exclusion chromatography was carried out on a polymer labo-
ratories PL 50 instrument equipped with two PLgel 5 μm
MIXED-C columns columns in THF in THF at 40 °C with an
RI detector. Data are referenced to linear polystyrene stan-
dards. Dynamic light scattering (DLS) on diluted dispersion
samples was performed on a Malvern Nano-ZS ZEN 3600 parti-
cle sizer (173° backscattering). The autocorrelation function
was analyzed using the Malvern dispersion technology software
5.10 algorithm to obtain volume- and number-weighted particle
size distributions and polydispersity indices (PDI). TEM images
were obtained on a Libra 120 instrument (acceleration voltage
120 kV). Conductivities were determined on compressed pellets
by the four-point method. Phenylacetylene (98%), tricyclohexyl-
phosphane, tri-n-butylphosphine (95%), and 1,4-dichlorobutane
(99%) were purchased from Acros, LiAlH4 was purchased from
Merck, and 1-hexene (97%) was purchased from Aldrich. SDS
(g96%) was purchased from Fluka. Dibromonomethyltriphenyl-
phosphonium bromide,36 4-(hexyloxy)-3-methoxybenzaldehyde,37
1,3-bis(di-tert-butylphosphino)propane,38 and 1,3-bis(di-n-hexyl-
phosphino)propane23d were prepared according to published
procedures.
Figure 2. DLS trace of a poly(phenylacetylene) dispersion from poly-
merization in microemulsion (entry 5-3).
Synthesis of 3-Methoxy-4-n-hexyloxyphenylacetylene (MHPA).
Under an argon atmosphere, 47.95 g of dibromonomethyltri-
phenylphosphonium bromide (93.1 mmol) and 9.92 g of tBuOK
(88.4 mmol) were dissolved in 450 mL of dry THF. The solution
was cooled to -80 °C and stirred for several minutes. 11.0 g of
4-(hexyloxy)-3-methoxybenzaldehyde (46.6 mmol) was added
in one batch, and the solution was warmed to room tempera-
ture. After 10 min, 26.1 g of tBuOK was added in one batch. The
solution was quenched with saturated brine (300 mL) and
extracted with ether. The combined organic layers were dried
over MgSO4, and the solvent was evaporated. The residue was
extracted with ether, the extract was filtered through diatom-
aceous earth, and the solvent was evaporated. The product
was purified by column chromatography (PE:ethyl acetate = 1:1)
to obtain 10.1 g of 4-ethynyl-1-(hexyloxy)-2-methoxybenzene
Figure 3. TEM of phenylacetylene particles from polymerization in
microemulsion (entry 5-3).
1
polyacetylene, the introduction of substituents on the main
chain strongly reduces conductivity. Conductivities around
10-5 S cm-1 were reported for poly(phenylacetylene) treated
with iodine.35 Also for the polyphenyacetylenes prepared
in this work, conductivities of 3ꢀ10-5 S cm-1 were observed
on iodine-“doped” compressed pellets. As an illustration of
the patterning of these reactive submicrometer particles, the
dispersion were printed with an inkjet printer to obtain photo-
quality resolution yellow images. Exposure to bromine converts
these to black-and-white style pictures due to the unsatu-
rated nature of the polymer (cf. Supporting Information).
(93%). H NMR (400 MHz, CDCl3): δ 7.07 (dd, J = 1.9, 8.3,
1H), 6.98 (d, J=1.9, 1H), 6.79 (d, J=8.3, 1H), 4.00 (t, J=6.9,
2H), 3.85 (s, 3H), 3.00 (s, 1H), 1.89-1.77 (m, 2H), 1.44 (dq, J=
7.1, 9.6, 2H), 1.33 (td, J=3.6, 7.2, 4H), 0.93-0.85 (m, 3H). 13
C
NMR (101 MHz, CDCl3): δ 149.68, 149.10, 125.63, 115.29,
114.16, 112.52, 84.07, 75.73, 69.15, 56.14, 31.74, 29.20, 25.78,
22.75, 14.19.
Synthesis of 1-Naphtylacetylene (NA). Under an argon atmo-
sphere, 65.94 g of dibromonomethyltriphenylphosphonium
bromide (128.1 mmol) and 13.6 g of tBuOK (121 mmol) were
dissolved in 600 mL of dry THF. The solution was cooled to -80 °C
and stirred for several minutes. 10.0 g of 1-naphthaldehyde
(64.0 mmol) was added at once, and the solution was warmed to
room temperature. After 10 min, 35.9 g of tBuOK was added at
once. The solution was quenched with saturated brine (500 mL)
and extracted with ether. The combined organic layers were dried
over MgSO4, and the solvent was evaporated. The residue was
Summary and Conclusions
Cationic palladium(II) complexes with a bidentate diphos-
phine ligand substituted with very bulky tert-butyl substituents
are highly active for catalytic polymerization of phenylacetylene

8722 Macromolecules, Vol. 43, No. 21, 2010
Huber and Mecking
extracted with ether and filtered through diatomaceous earth,
and the filtrate was evaporated. The product was purified by
column chromatography (PE:ethyl acetate 1:1) to obtain 6.81 g
References and Notes
(1) (a) Urban, D.; Takamura, K. Polymer Dispersions and Their
Industrial Applications; Wiley-VCH: Weinheim, 2002. (b) van Herk,
A. M. Chemistry and Technology of Emulsion Polymerisation;
Blackwell Publishing: Oxford, 2005. (c) Fitch, R. M. Polymer Col-
loids; Academic Press: San Diego, 1997. (d) Lovell, P. A.; El-Aasser,
M. S. Emulsion Polymerization and Emulsion Polymers; Wiley:
Chichester, 1997.
1
of 4-ethinyl-1-(hexyloxy)-2-methoxybenzene (70%). H NMR
(400 MHz, CDCl3): δ 8.42 (d, J=8.4, 1H), 7.88 (d, J=8.2, 2H),
7.79 (dd, J=1.0, 7.1, 1H), 7.59 (dddd, J=1.3, 6.9, 8.2, 26.5, 2H),
7.46 (dd, J = 7.2, 8.3, 1H), 3.52 (s, 1H). 13C NMR (101 MHz,
CDCl3): δ 133.70, 133.27, 131.42, 129.47, 128.48, 127.14, 126.67,
126.23, 125.28, 119.96, 82.19, 81.96.
(2) Pecher, J.; Mecking, S. Chem. Rev. 2010, in press (doi 10.1021/
cr100132y).
Synthesis of 1,4-Bis(di-tert-butylphosphino)butane. In a 100 mL
Schlenk tube, 5.0 g of di-tert-butylphosphine (34 mmol) was
dissolved in 30 mL of Et2O, and the mixture was cooled to 0 °C
in an ice bath. Within 10 min, 23.90 mL of tBuLi (1.5 M solution
in hexane, 35.9 mmol) was added dropwise. 2.246 g of 1,4-
dichlorobutane (17.68 mmol) was added in a single batch,
upon which the solution became pale yellow. The solution was
stirred for 20 min at 0 °C and another hour at room temperature.
The solvent was removed, and 10 mL of hexane followed by
10 mL of water was added. The organic layer was extracted three
times with 10 mL of hexane each. From the combined organic
layers the solvent was evaporated, and the crude product
was purified by Kugelrohr distillation at 130 °C (0.2 mbar) to
obtain 4.05 g of 1,4-bis(di-tert-butylphosphino)butane (85%).
1H NMR (400 MHz, C6D6, 25 °C): δ/ppm=1.72 (m, 4H), 1,33
(m, 4H), 1.03 (d, 36H, 3JHP = 10,8 Hz). 31P NMR (162 MHz):
δ 29.0.
Preparation of Catalyst Solution (Example). A solution of
33.7 mg (150 μmol) of Pd(OAc)2 in 5 mL of acetonitrile and a
solution of 149.5 mg (450 μmol) of 1,3-bis(di-tert-butylphos-
phino)propane in 5 mL of ethanol were mixed, and the solvent
was evaporated in vacuo. The residue was dissolved in a mixture
of 0.2 mL of ethanol and 4.8 mL of hexane to afford a catalyst
solution with a concentration of 30 μmol Pd/mL.
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Miniemulsion Polymerization Procedure. In a 100 mL round-
bottom Schlenk flask closed with a septum, an aqueous solution
of 0.5 g of SDS in 39 g of water was topped with a layer of 10 mL
of phenylacetylene. To this layer 1.0 mL of catalyst solution
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followed by addition of one drop of methanesulfonic acid while
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100 mL of methanol, followed by filtration through a nylon filter
(0.45 μm pore size). The polymer was washed with methanol and
dried at room temperature.
Microemulsion Polymerization Procedure. In a 100 mL round-
bottom Schlenk flask closed with a septum, a mixture of 3.0 g of
phenylacetylene, 4.0 g of SDS, 4.0 g of pentanol, and 44.5 g of
water was stirred overnight to afford a clear microemulsion. In a
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of pentanol were mixed with 1.0 mL of catalyst solution
(20 μmol/mL) and stirred for 5 min to afford a clear microemul-
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was transferred to the monomer microemulsion. After 1 min of
stirring, one drop of methanesulfonic acid was added to the mixture.
After 1 h of polymerization, an intensely orange-colored latex
was obtained.
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Acknowledgment. Financial support by the DFG (Me1388/
7-1) is gratefully acknowledged. We thank Marina Krumova for
TEM analyses and Lars Bolk for GPC analyses. S.M. is indebted
to the Fonds der Chemischen Industrie and to the Hermann-
Schnell Foundation.
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Supporting Information Available: Images of inkjet print-
outs with the dispersions. This material is available free of charge
via the Internet at http://pubs.acs.org.

Article
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