Accelerated Synthesis of Poly(methyl methacrylate)-bPoly(vinyl chloride)-b-Poly(methyl methacrylate) Block
Copolymers by the CuCl/Tris(2-dimethylaminoethyl)amineCatalyzed Living Radical Block Copolymerization of Methyl
Methacrylate Initiated with ␣,␻-Di(iodo)poly(vinyl
chloride) in Dimethyl Sulfoxide at 90 °C
VIRGIL PERCEC, TAMAZ GULIASHVILI, ANATOLIY V. POPOV, ERNESTO RAMIREZ-CASTILLO,
JORGE F. J. COELHO, LUIS A. HINOJOSA-FALCON
Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia,
Pennsylvania 19104-6323
Received 4 October 2004; accepted 22 October 2004
DOI: 10.1002/pola.20616
Publoshed online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: ␣,␻-Di(iodo)poly(vinyl chloride)s [␣,␻-di(iodo)PVCs] with number-average molecular weights ranging from 2100 to 20,000 and weight-average molecular weight/number-average molecular weight ratios ranging from 1.72 to 2.16 were synthesized through
the single-electron-transfer/degenerative-chain-transfer mediated living radical polymerization of vinyl chloride initiated with iodoform and catalyzed by sodium dithionite in water
at 25–35 °C. These ␣,␻-di(iodo)PVCs were used as macroinitiators for the metal-catalyzed
living radical block copolymerization of methyl methacrylate to produce poly(methyl
methacrylate)-b-poly(vinyl chloride)-b-poly(methyl methacrylate) block copolymers. By
searching various copper derivatives, ligands, and solvents, it has been found that CuCl/
tris(2-dimethylaminoethyl)amine in dimethyl sulfoxide at 90 °C provides an accelerated
method for the synthesis of block copolymers. Poly(methyl methacrylate)-b-poly(vinyl chloride)-b-poly(methyl methacrylate) block copolymers with number-average molecular
weights of 41,000 –106,700 were produced by this method in 30 – 80 min. These reaction
times were within the range of induction times exhibited when the same block copolymers
were synthesized with CuCl/2,2⬘-bipyridine in diphenyl ether at 90 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1649 –1659, 2005
Keywords: block copolymers; kinetics (polym.); living polymerization; poly(methyl
methacrylate); poly(vinyl chloride) (PVC); radical polymerization
INTRODUCTION
In a previous publication,1 we reported that ␣,␻di(iodo)poly(vinyl chloride) [␣,␻-di(iodo)PVC],
Correspondence
upenn.edu)
to:
V.
Percec
(E-mail:
percec@sas.
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 43, 1649 –1659 (2005)
© 2005 Wiley Periodicals, Inc.
synthesized by the single-electron-transfer/degenerative-chain-transfer mediated living radical
polymerization (SET–DTLRP) of vinyl chloride
(VC),2–5 can be used as a macroinitiator for the
metal-catalyzed living radical block copolymerization of methyl methacrylate (MMA) to produce
poly(methyl methacrylate)-b-poly(vinyl chloride)b-poly(methyl methacrylate) (PMMA-b-PVC-bPMMA) block copolymers. These PMMA-b-PVC1649
1650
PERCEC ET AL.
Figure 1. Influence of the copper derivative on the copper-derivative/bpy-catalyzed
living radical block copolymerization of MMA initiated with ␣,␻-di(iodo)PVC (I) with
Mn ⫽ 2100: (a) [CuCl]0/[bpy]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol in Ph2O at 90
°C, (b) [Cu(0)]0/[bpy]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol in DMSO at 90 °C, and
(c) [Cu2Te]0/[bpy]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol in Ph2O at 90 °C. kp is the
rel
apparent rate constant of propagation, Mth is the theoretical molecular weight, and Ieff
is the relative initiator efficiency.
b-PMMA block copolymers exhibit molecular
weight distributions [weight-average molecular
weight/number-average molecular weight (Mw/
Mn)] lower than 1.20 and incorporate a variety of
molecular weights for both the poly(methyl
methacrylate) (PMMA) and poly(vinyl chloride)
(PVC) segments. This synthetic method provides
the first general strategy for the synthesis of ABA
and AB block copolymers containing PVC in the A
or B block and a variety of polymer structures
derived from methacrylates, acrylates, acrylonitrile, and styrenes in the second block. In addition, more complex block copolymers and other
architectures have become available for the first
time by using various combinations of the SET–
DTLRP of VC and other monomers and the metalcatalyzed living radical polymerization of acrylates,6 –10 acrylonitrile,8,11 methacrylates,6 – 8,12
and styrenes.6 – 8,12 Finally, ␣,␻-di(iodo)PVC obtained by the SET–DTLRP of VC is free of structural defects and so exhibits, both as a homopolymer and in block copolymers based on it, much
higher thermal stability than current commercial
PVC.4,5 This combination of novel physical properties and architectures13–16 opens novel technological opportunities for PVC-based materials.
The aforementioned block copolymerization
method1 uses ␣,␻-di(iodo)PVC as an initiator and
ACCELERATED SYNTHESIS OF PMMA-b-PVC-b-PMMA
1651
Table 1. Influence of the Nature of the Catalyst on the Rate of Block Copolymerization
and on the Mn and Mw/Mn Values of PMMA-b-PVC-b-PMMA Synthesized by Initiation from
␣,␻-Di(Iodo)PVC (Mn ⫽ 2100 and Mw/Mn ⫽ 1.84) in Ph2O at 90 °Ca
1
2
3
4
Catalyst
kpexp (min⫺1)c
Conversion
(%)/Time (min)
Mn (GPC)
Mw/Mn
Ieff (%)d
CuCl/bpy
Cu2Te/bpy
Cu(0)bpy
Cu(0)/bpyb
0.033
0.022
0
0.021
95/110
81/80
0
63/50
46,500
150,000
0
93,000
1.19
1.22
—
1.29
38.5
9.3
11.7
[Metal catalyst]0/[bpy]0/[␣,␻-di(iodo)PVC]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol; [MMA]0 ⫽ 6.4 mol/L.
The reaction was performed in DMSO.
Experimental rate constant of propagation.
d
Initiator efficiency.
a
b
c
CuCl/2,2⬘-bipyridine (bpy) as a catalyst. Polymerdium dithionite (Na2S2O4) at 25–35 °C in H2O by
a method reported from our laboratory.4
ization experiments were carried out at 90 °C in
the presence of some diphenyl ether (Ph2O),
which was used to lower the viscosity of the reacInfluence of the Copper/bpy Catalyst on the Rate
tion mixture and thus to facilitate the kinetic
of the Block Copolymerization of MMA
analysis of the block copolymerization process.
This block copolymerization is accompanied by an
The efficiency of various copper/bpy catalysts on
induction period because at its beginning the rethe living radical block copolymerization of
action mixture is heterogeneous. For fundamenMMA initiated from the chain ends of ␣,␻tal and technological reasons, an accelerated syndi(iodo)PVC with Mn ⫽ 2100 and Mw/Mn ⫽ 1.84
thetic method would be highly desirable. In this
was investigated with kinetic experiments carpublication, we survey various synthetic strateried out at 90 °C with Ph2O as the diluent. All
gies in order to generate an accelerated method
block copolymerization experiments were perfor block copolymerization initiated from the
formed in 25-mL Schlenk tubes. Because PVC is
chain ends of ␣,␻-di(iodo)PVC. Toward this goal
not soluble in MMA or Ph2O, at the beginning of
we have investigated various copper-based catathe polymerization, the reaction mixture was
lytic systems while maintaining bpy as the ligand
heterogeneous. As the conversion increased, the
and Ph2O as the solvent, with different solvents
resulting PMMA-b-PVC-b-PMMA became solufor the CuCl/bpy catalytic system and different
ble in MMA and Ph2O, and as a result, the
ligands for CuCl. An accelerated block copolymerreaction mixture became homogeneous. CuCl/
ization of MMA with CuCl/tris(2-dimethylaminoethyl)bpy,17 Cu(0)/bpy,15,18 –21 and copper(I) telluride
amine (Me6-TREN) as the catalyst and dimethyl
(Cu2Te)/bpy22 were investigated as catalysts in
sulfoxide (DMSO) as the diluent at 90 °C is rethese block copolymerization experiments.
ported here. This synthetic method eliminates the
Cu(0)2,3,15,18 –21 and Cu2Te2,3,22 are self-reguinduction time of the block copolymerization and
lated catalytic systems because they are precurproduces PMMA-b-PVC-b-PMMA in conversions
sors that generate in situ an extremely reactive
higher than 90% in 30 – 80 min.
nascent catalyst as a molecular dispersion and
in the minimum required concentration. Therefore, Cu2Te, Cu2O, Cu2S,15,18 –22 and other reRESULTS AND DISCUSSION
lated catalysts23 were able to eliminate side
reactions taking place with the CuCl catalyst
Synthesis of ␣,␻-Di(iodo)PVC
and subsequently were used in the synthesis of
␣,␻-Di(iodo)PVCs with number-average molecupolymers with complex architectures.13–16
lar weights (Mn’s) ranging from 2100 to 20,000
The kinetic analysis of these block copolymerand Mw/Mn values ranging from 1.72 to 2.16 were
ization experiments is shown in Figure 1. The
synthesized through the SET–DTLRP of VC iniCuCl/bpy-mediated block copolymerization of
tiated with iodoform (CHI3) and catalyzed by soMMA in Ph2O exhibited an induction period of
1652
PERCEC ET AL.
Figure 2. Influence of the solvent on the CuCl/bpy-catalyzed living radical block
copolymerization of MMA initiated with ␣,␻-di(iodo)PVC (I) with Mn ⫽ 2100 at 90 °C
([CuCl]0/[bpy]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol): (a) Ph2O, (b) DMSO, (c)
cyclohexanone, and (d) (CH2)2CO3. kp is the apparent rate constant of propagation, Mth
rel
is the theoretical molecular weight, and Ieff
is the relative initiator efficiency.
about 30 min [Fig. 1(a)]. Cu(0)/bpy did not initiate
the block copolymerization of MMA from the
chain ends of ␣,␻-di(iodo)PVC when Ph2O was
used as a solvent (Table 1). However, when Cu(0)/
bpy was used as a catalyst in DMSO, the block
polymerization of MMA initiated from ␣,␻-di(iodo)PVC did not exhibit an induction period and
proceeded with an apparent rate constant of prop-
1653
ACCELERATED SYNTHESIS OF PMMA-b-PVC-b-PMMA
Table 2. Influence of the Solvent on the Rate of Block Copolymerization and on the Mn and Mw/Mn Values of
PMMA-b-PVC-b-PMMA Synthesized by Initiation from ␣,␻-Di(Iodo)PVC (Mn ⫽ 2100 and Mw/Mn ⫽ 1.84)a
1
2
3
4
Solvent
kpexp (min⫺1)b
Mn (GPC)/Conversion
(%)
Mw/Mn
Ieff (%)c
Ph2O
DMSO
Cyclohexanone
(CH2)2CO3
0.033
0.021
0.015
0.031
46,500/95
28,800/89
23,200/70
30,200/90
1.20
1.21
1.28
1.16
38.5
63.0
61.7
69.0
[CuCl]0/[bpy]0/[␣,␻-di(iodo)PVC]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol; temperature ⫽ 90 °C; [MMA]0 ⫽ 6.4 mol/L.
Experimental rate constant of propagation.
c
Initiator efficiency.
a
b
agation almost identical to that of the CuCl/bpycatalyzed process in Ph2O [Fig. 1(b) and Table 1].
Cu2Te/bpy also initiated this block copolymerization without an induction period [Fig. 1(c)] and
mediated its rate almost as quickly as CuCl/bpy
(Table 1). Most likely, CuI/bpy was generated in
situ with the Cu(0)/bpy and Cu2Te/bpy catalysts.
Moreover, Cu(0)/bpy in DMSO and Cu2Te/bpy in
Ph2O produced PMMA-b-PVC-b-PMMA with molecular weight distributions as narrow as those of
PMMA-b-PVC-b-PMMA generated by the CuCl/
bpy-catalyzed block copolymerization (Table 1).
The mechanisms of the CuCl/bpy-, Cu(0)/bpy-,
and Cu2Te/bpy-mediated block copolymerizations
are most likely different. In the case of CuCl/bpy,
a potential exchange between PMMA dormant
propagating species containing alkyl iodide and
alkyl chloride may occur. However, in the case of
Cu(0)/bpy and Cu2Te/bpy, only alkyl iodide
PMMA dormant species are possible. The mechanism of this reaction is under investigation and
will be reported in due time.
Influence of the Polymerization Solvent on the
Rate of the Block Copolymerization of MMA
For block copolymerization mediated by Cu(0)/
bpy, we observed a great difference between the
experiments performed in Ph2O and those
performed in DMSO. Therefore, we decided to
consider the influence of four different solvents—
Ph2O, DMSO, cyclohexanone, and ethylene carbonate [(CH2)2CO3]— on the block copolymerization experiment catalyzed by CuCl/bpy. The influence of the solvent on the CuCl/bpy-catalyzed
block copolymerization of MMA initiated from the
chain ends of ␣,␻-di(iodo)PVC was investigated
with the aid of kinetic experiments. These kinetic
experiments are shown in Figure 2. The first im-
portant conclusion derived from the data presented in Figure 2 is that although the polymerization performed in Ph2O exhibited an induction
period [Fig. 2(a)], all the other solvents eliminated this induction period. The rate of block
copolymerization decreased only slightly when
the solvent was changed from Ph2O to DMSO and
was almost half for cyclohexanone (Fig. 1 and
Table 2). However, the use of (CH2)2CO3 produced
a higher rate of block copolymerization that even
Ph2O [Fig. 2(a,d) and Table 2]. Moreover, the
molecular weight distributions of the final
PMMA-b-PVC-b-PMMAs were almost identical,
in light of the differences in the final conversions
[Table 2 and Figure 1(a– c)]. (CH2)2CO3 seemed to
be the only solvent that increased the rate of block
copolymerization while producing a block copolymer with a lower molecular weight distribution
(Table 2 and Fig. 2). Because of these results, we
decided to investigate the role of the ligand in the
CuCl-mediated block copolymerization of MMA
initiated from the chain ends of ␣,␻-di(iodo)PVC
in DMSO.
Influence of the CuCl Ligand on the Block
Copolymerization of MMA Initiated from the
Chain Ends of ␣,␻-Di(iodo)PVC in DMSO
The influence of five different ligands— bpy, Me6TREN, hexamethyltriethylenetetramine (HMTETA),
poly(ethylene imine) (PEI), and methylated poly(ethylene imine) (MePEI)— on the CuCl-catalyzed
block copolymerization of MMA initiated from the
chain ends of ␣,␻-di(iodo)PVC was investigated
with kinetic experiments (Figs. 3 and 4). As already discussed in the previous subsection,
DMSO eliminated the induction period for the
CuCl/bpy process [Fig. 3(a)]. Me6-TREN increased the rate of block copolymerization by a
1654
PERCEC ET AL.
Figure 3. Influence of the ligand on the CuCl/ligand-catalyzed living radical block
copolymerization of MMA initiated with ␣,␻-di(iodo)PVC (I) with Mn ⫽ 2100 at 90 °C
([CuCl]0/[ligand]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol): (a) bpy in DMSO, (b)
Me6-TREN in DMSO, (c) Me6-TREN in Ph2O, and (d) HMTETA in DMSO. kp is the
rel
apparent rate constant of propagation, Mth is the theoretical molecular weight, and Ieff
is the relative initiator efficiency.
factor of four in comparison with CuCl/bpy and
maintained a reasonably low molecular weight
distribution [Fig. 3(b)]. A very interesting result
was that Me6-TREN also eliminated the induction period when the block copolymerization was
carried out in Ph2O [Fig. 2(b,c)]. However, the
ACCELERATED SYNTHESIS OF PMMA-b-PVC-b-PMMA
1655
Figure 4. Influence of the ligand on the CuCl/ligand-catalyzed living radical block
copolymerization of MMA initiated with ␣,␻-di(iodo)PVC (I) with Mn ⫽ 2100 in DMSO
at 90 °C ([CuCl]0/[ligand]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol): (a) PEI in DMSO,
(b) MePEI, and (c) no ligand. kp is the apparent rate constant of propagation, Mth is the
rel
theoretical molecular weight, and Ieff
is the relative initiator efficiency.
molecular weight distribution of PMMA-b-PVCb-PMMA was substantially broader when the
block copolymer was prepared with Me6-TREN
in Ph2O versus DMSO [Fig. 3(b,c) and Table 3].
CuCl/HMTETA also produced a higher rate
than CuCl/bpy. Nevertheless, this increase was
only by a factor of 1.5 [Fig. 3(d) and Table 3].
Commercial and inexpensive PEI and its permethylated derivative also increased the rate of
block copolymerization by a factor of more than
three in comparison with CuCl/bpy [Fig. 4(a,b)
and Table 3]. One of the most interesting results generated by these experiments was that
in DMSO, CuCl catalyzed the block copolymerization of MMA initiated from the active chain
ends of ␣,␻-di(iodo)PVC even in the absence of a
ligand [Fig. 4(c)]. The molecular weight distribution of PMMA-b-PVC-b-PMMA obtained in
the absence of a ligand was as narrow as the one
obtained in the presence of a ligand (Table 3).
However, the rate of block copolymerization
was, almost by an order of magnitude, lower
than the one obtained in the presence of bpy
(Table 3). An interesting conclusion drawn from
these experiments is that with Me6-TREN or
PEI as the ligand in the CuCl-catalyzed block
copolymerization of MMA initiated from the
chain ends of PMMA-b-PVC-b-PMMA, block copolymers can be obtained with greater than
90% conversions in 30 min. This is remarkable
1656
PERCEC ET AL.
Table 3. Influence of the Nature of the Ligand on the Rate of Block Copolymerization
and on the Mn and Mw/Mn Values of PMMA-b-PVC-b-PMMA Synthesized by Initiation
from ␣,␻-Di(Iodo)PVC (Mn ⫽ 2100 and Mw/Mn ⫽ 1.84)a
1
2
3
4
5
6
7
Ligand
kpexp (min⫺1)c
Mn (GPC)/Conversion
(%)
Mw/Mn
Ieff
(%)d
bpy
Me6-TREN
Me6-TRENb
HMTETA
PEI
MePEI
No ligand
0.021
0.084
0.087
0.037
0.069
0.059
0.003
28,800/89
41,400/92
34,900/93
45,600/89
89,000/87
47,500/92
45,000/47
1.21
1.33
1.73
1.23
1.25
1.26
1,24
63.0
52.9
58.2
38.7
19.5
40.2
22.7
[CuCl]0/[ligand]0/[PVC]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol; solvent ⫽ DMSO; temperature ⫽ 90 °C; [MMA]0 ⫽ 6.4 mol/L.
Ph2O was used as the solvent.
c
Experimental rate constant of propagation.
d
Initiator efficiency.
a
b
progress because in the previous procedure
based on CuCl/bpy in Ph2O, the induction time
itself is about 30 min.
CuCl/Me6-TREN-Catalyzed Living Radical Block
Copolymerization of MMA Initiated from the
Chain Ends of ␣,␻-Di(iodo)PVC (Mn
ⴝ 2100 –20,000) in DMSO at 90 °C
CuCl/Me6-TREN in DMSO at 90 °C was used to
investigate the synthesis of PMMA-b-PVC-bPMMA block copolymers by the living radical
block copolymerization of MMA initiated from
␣,␻-di(iodo)PVC (Mn ⫽ 2100 –20,000 and Mw/Mn
⫽ 1.72–2.16). Kinetic experiments for five samples of ␣,␻-di(iodo)PVC are shown in Figures 5
and 6. Regardless of the molecular weight of the
␣,␻-di(iodo)PVC initiator, the block copolymerization experiments did not exhibit any induction
period. In all cases, PMMA-b-PVC-b-PMMAs
with Mw/Mn values ranging from 1.30 to 1.52
were obtained at an MMA conversion of 92–78%.
The reaction times of these block copolymerization experiments varied from 30 to 80 min (Table 4 and Figs. 5 and 6). These reaction times
were within the range of induction times exhibited by the block copolymerizations catalyzed by
CuCl/bpy in Ph2O at the same temperature, that
is, 90 °C.
We believe that the CuCl/Me6-TREN-catalyzed
living radical block copolymerization of MMA in
DMSO at 90 °C proceeds by a combination of
competitive activation and deactivation mediated
by Cu(I)/Cu(II) species, single-electron transfer,
and degenerative chain transfer. During this process, an exchange of dormant and active species
may also take place. Investigations to clarify the
mechanism of this synthetic procedure are in
progress in our laboratory.
CONCLUSIONS
An investigation of the influence of various copper
catalysts, polymerization solvents, and ligands on
the metal-catalyzed living radical block copolymerization of MMA initiated from the chain ends
of ␣,␻-di(iodo)PVC has been described. CuCl/Me6TREN in DMSO at 90 °C was selected for this
synthetic method because it accelerates the CuCl/
bpy-catalyzed living radical block copolymerization of MMA initiated from the chain ends of
␣,␻-di(iodo)PVC in Ph2O at 90 °C.1
From ␣,␻-di(iodo)PVCs with Mn values ranging
from 2100 to 20,000, PMMA-b-PVC-b-PMMAs
with Mn values of 41,000 –106,700 and Mw/Mn
values of approximately 1.30 were obtained
within 30 – 80 min. These reaction times were in
the same range as the induction times exhibited
by the block copolymerization of MMA initiated
from ␣,␻-di(iodo)PVC and catalyzed by CuCl/bpy
in Ph2O at 90 °C. In addition, the initiation efficiency, determined from kinetic plots, though calculated with PMMA-based molecular weights, increased as Mn of ␣,␻-di(iodo)PVC increased. This
trend confirms results reported elsewhere.1
ACCELERATED SYNTHESIS OF PMMA-b-PVC-b-PMMA
1657
Figure 5. CuCl/Me6-TREN-catalyzed living radical block copolymerization of MMA
initiated with ␣,␻-di(iodo)PVC (I) with different Mn values in DMSO at 90 °C ([CuCl]0/
[Me6-TREN]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol): (a) Mn ⫽ 2100, (b) Mn ⫽ 5500,
and (c) Mn ⫽ 9200. kp is the apparent rate constant of propagation, Mth is the
rel
theoretical molecular weight, and Ieff
is the relative initiator efficiency.
EXPERIMENTAL
Materials
Copper powder (99%), tris(2-aminoethyl)amine
(96%), PEI (a mixture of linear and branched
chains; Mn ⬇ 423, bp ⫽ 250 °C), HMTETA
(⬎97%), cyclohexanone (⬎99%), (CH2)2CO3
(98%), Ph2O (⬎99%), and formic acid (99%) were
purchased from Aldrich and were used as received. Cu2Te (99.5%) was purchased from Alfa
Aesar. MMA (⬎99%; Aldrich) was passed through
a basic Al2O3 chromatographic column (flash) before use. CuCl (⬎99%; Aldrich) was washed with
4% HCl two times, filtered under argon, rinsed
with degassed deionized water and tetrahydrofuran (THF), dried in vacuo, and stored under ar-
gon. CHI3 (99%) and Na2S2O4 (85%) were purchased from Lancaster. THF (99%), methylene
chloride (99.5%), methanol (99.8%), DMSO (99%),
and sodium bicarbonate (⬎99%) were purchased
from Fisher Scientific. Bpy (99%; Acros Organics)
was used as received. ␣,␻-Di(iodo)PVCs of different
molecular weights were prepared as described elsewhere.4 Me6-TREN was prepared as described
elsewere.24,25 All other chemicals were purchased
from Aldrich and were used as received.
Techniques
1
H NMR spectra (500 MHz) were recorded on a
Bruker DRX500 at 32 °C in CD2Cl2 and CDCl3
with tetramethylsilane as an internal standard.
1658
PERCEC ET AL.
Figure 6. CuCl/Me6-TREN-catalyzed living radical block copolymerization of MMA
initiated with ␣,␻-di(iodo)PVC (I) with different Mn values in DMSO at 90 °C ([CuCl]0/
[Me6-TREN]0/[I]0/[MMA]0 ⫽ 2/6/1/188 mol/mol/mol/mol): (a) Mn ⫽ 14,100 and (b) Mn
⫽ 20,000. kp is the apparent rate constant of propagation, Mth is the theoretical
rel
molecular weight, and Ieff
is the relative initiator efficiency.
Gel permeation chromatography (GPC) analysis
was performed on a PerkinElmer series 10 highpressure liquid chromatograph equipped with an
LC-100 column oven (40 °C), a Nelson Analytical
900 series integrator data station, a PerkinElmer
785A ultraviolet–visible detector (254 nm), a Varian Star 4090 refractive-index detector, and two
AmGel columns (10 ␮m and 500 Å and 10 ␮m and
104 Å). THF (Fisher; high-pressure-liquid-chromatography-grade) was used as an eluent at a
flow rate of 1 mL/min. The Mn and Mw values
were determined versus PMMA standards.
The glass-transition temperatures were determined on a Thermal Analysis TA-2920 modulated
Table 4. Influence of Mn of the ␣,␻-Di(Iodo)PVC Macroinitiator on the Rate of Block Copolymerization
of MMA and on the Properties of PMMA-b-PVC-b-PMMAa
␣,␻-Di(Iodo)PVC
1b
2b
3c
4c
5d
PMMA-b-PVC-b-PMMA
kpexp (min⫺1)e
Mn (GPC)
Mw/Mn
Mn (GPC)/Conversion
(%)/Time (min)
Mw/Mn
Ieff (%)f
0.084
0.082
0.036
0.040
0.021
2100
5,500
9,200
14,100
20,000
1.84
1.74
1.80
1.72
2.16
41,000/92/30
58,900/92/30
57,400/83/45
84,500/85/45
106,700/78/45
1.33
1.33
1.30
1.31
1.51
52.9
40.0
66.1
33.9
81.8
[CuCl]0/[Me6-TREN]0/[␣,␻-di(iodo)PVC]0 ⫽ 2/6/1 mol/mol/mol; solvent ⫽ DMSO; temperature ⫽ 90 °C.
[MMA]0 ⫽ 6.4 M; [MMA]0/[␣,␻-di(iodo)PVC]0 ⫽ 188
c
[MMA]0 ⫽ 3.76 M; [MMA]0/[␣,␻-di(iodo)PVC]0 ⫽ 376.
d
[MMA]0 ⫽ 2.68 M; [MMA]0/[␣,␻-di(iodo)PVC]0 ⫽ 940.
e
Experimental rate constant of propagation.
f
Initiator efficiency.
a
b
ACCELERATED SYNTHESIS OF PMMA-b-PVC-b-PMMA
differential scanning calorimeter. In all cases, the
heating and cooling rates were 5 °C/min.
Synthesis of Permethylated PEI
A mixture of 4.23 g of PEI (molecular weight
⬃ 423; 10 mmol), 13.8 g of formic acid, 9.0 g of
formaldehyde (37% water solution), and 10 mL of
water was heated for 12 h at 120 °C (oil bath)
under stirring. All volatiles were removed under
reduced pressure (20 Torr) at 40 °C. The residue
was dissolved in 100 mL of 15% KOH in water
and extracted with diethyl ether (2 ⫻ 100 mL).
The ethereal layer was dried over MgSO4 and
then filtered. After rotary evaporation, 5.0 g
(87%) of a yellowish oil was obtained and used
without further purification.
Typical Procedure for the Block Copolymerization
of ␣,␻-Di(iodo)PVC with MMA
The ␣,␻-di(iodo)PVC macroinitiator (Mn ⫽ 2100
and Mw/Mn ⫽ 1.84; 105 mg, 0.05 mmol), CuCl (9.9
mg, 0.1 mmol), Me6-TREN (69.0 mg, 0.3 mmol),
MMA (1.0 mL, 9.4 mmol), and DMSO (0.5 mL)
were placed in a 25-mL Schlenk tube. The tube
was sealed (a rubber septum with a screw cap).
The reaction mixture was degassed with standard
freeze–pump–thaw cycles, and the tube was
charged with dry argon. The reaction mixture was
kept at 90 ⫾ 0.1 °C under stirring and sampled
with an airtight syringe at predetermined times.
The monomer conversion was determined by 500MHz 1H NMR spectroscopy, whereas the Mn and
Mw/Mn values were determined by GPC with respect to PMMA standards. The polymerization
was stopped after 30 min, and the reaction mixture was dissolved in 18 mL of THF and precipitated in 100 mL of a water/MeOH mixture (1:2
v/v). The precipitated polymer was filtered and
dried.
The financial support of the Edison Polymer Innovation
Corp., the PVC Technology Consortium, and the National Science Foundation is gratefully acknowledged.
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