Supporting Information
RAFT Cryopolymerizations of N, N-dimethylacrylamide and
N-isopropylacrylamide in Moderately Frozen Aqueous Solution
Xiao-Li Sun, Wei-Dong He*, Jian Li, Li-Ying Li, Bo-Yu Zhang, Ting-Ting Pan
Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter
Chemistry, University of Science and Technology of China, Hefei, Anhui 230026,
China
1H
1
NMR Analysis of mPEG-DMP Macro-CTA
H NMR spectra of mPEG-DMP is shown in Figure S1, where the signal of
methylene protons in mPEG is observed at 3.62 ppm, and that of methyl protons in
DMP residue is visible at 0.87 ppm. The signal of methylene protons adjacent to
trithiocarbonate group in DMP residue appears at 3.4 ppm and the signals of other
methylene protons in DMP residue appear in the range of 1.2~1.3 ppm. The
end-functionality of this macro-CTA was 100 % based on the integral ratio of the
signal at 0.87 ppm to that at 3.62 ppm.
1
O
b
C10H21
a
S
c
S
S
d
f
e
O
O
f
d
g
nO
f
b
g
e
7
6
5
d
a
c
4
3
2
1
0
Chemical Shift/ppm
Figure S1. 1H NMR spectra of mPEG-DMP macro-CTA.
1H
NMR Analysis of PDMA, PEG-b-PDMA, and Chain Extension Polymers of
PDMA-b-PNIPAM-b-PDMA and PEG-b-PDMA-b-PNIPAM.
Typical
1
H NMR spectra of PDMA (from CMP) and PEG-b-PDMA (from
mPEG-DMP) are shown in Figure S2. The signal of methyl protons attached to the
amide group in DMA units is observed at 2.8-3.2 ppm, the methine group of DMA
unit attached to trithiocarbonate group is visible at 5.1 ppm. From the integrals of the
signal at 5.1 ppm and the signals between 1.0~3.3 ppm, the number-averaged
molecular weight (Mn,NMR) of PDMA at different sampling was calculated. As for
PEG-b-PDMA, the signal of methylene protons in PEG units is also observed at 3.6
ppm. Thus, Mn,NMR of PEG-b-PDMA was calculated based on the integrals of signals
between 1.0~3.3 ppm and those at 3.6 ppm, plus the number-averaged molecular
weight of mPEG-DMP (known as 5346).
2
O
C10H21
S
e
c
d O
b
S
O
S
O
m
O
N
n CH3
a
N
d
CH3 CH3 CH3 CH3
H2 O
a
PEG-b-PDMA
c
b
e
O
O
b S
HO
S
m
O
O
N
N
CH3 CH3 CH3 CH
a
OH
m
O
O
S
N
N
CH3 CH3 CH3 CH3
a
PDMA
b
9
8
7
6
5
4
3
2
1
0
Chemical Shift (ppm)
O
C11H23
S
c
S
p
O
HN
S
HN
O
m
O
O
O
c
n CH3
e
N
d
CH3 CH3
a
e
PEG-b-PDMA-b-PNIPAM
a
d
c
O
O
S
HO
m
O
O
N
S
p
O
p
O
NH
O
S
NH
HN
HN
d
CH3 CH3
OH
a
PDMA-b-PNIPAM-b-PDMA
d
9
8
7
e
N
CH3 CH3
e
a
m
O
6
5
4
3
2
1
0
Chemical Shift (ppm)
Figure S2. Typical of 1H NMR spectra of trithiocarbonate-capped PDMA (Conv =
87 %), PEG-b-PDMA (Conv = 88 %), PDMA-b-PNIPAM-b-PDMA and
PEG-b-PDMA-b-PNIPAM.
Figure S2 also shows the
PEG-b-PDMA-b-PNIPAM
1
H NMR spectra of PDMA-b-PNIPAM-b-PDMA and
triblock
copolymers
obtained
from
RAFT
3
cryopolymerization of NIPAM mediated by PDMA (Conv = 87 %) and
PEG-b-PDMA (Conv = 88 %) macro-CTAs. The observed characteristic peaks of
PNIPAM and PDMA demonstrate the successful chain extension polymerization.
1H
NMR Analysis of PNIPAM, PEG-b-PNIPAM, and Chain Extension Polymers
of PNIPAM-b-PDMA-b-PNIPAM and PEG-b-PNIPAM-b- PDMA.
Typical 1H NMR spectra of trithiocarbonate-functionalized PNIPAM (from CMP)
and PEG-b-PNIPAM (from mPEG-DMP) are similar with those of PDMA. The
characteristic signal of methine group in NIPAM unit is observed at 4.0 ppm.
RAFT Aqueous Polymerizations of DMA with mPEG-DMP or CMP as CTA at
Room Temperature.
RAFT cryopolymerizations exhibited different kinetic behaviors depending on the
monomer and CTA used. Thus, we investigated RAFT aqueous polymerizations at
room temperature to make a comparison. They were carried out with the same
polymerization procedure and recipe as the cryopolymerizations reported in the main
manuscript, except the temperature.
The pseudo-first-order kinetic plots for the CMP and mPEG-DMP mediated
polymerizations of DMA and NIPAM at 25 °C are summarized in Figure S3. For all
polymerizations, linear pseudo-first-order kinetics is observed, even at high monomer
conversions (≥ 90%). Thus, the apparent rate constants (kapp) and induction durations
(Tind) of the polymerizations by linear fitting of experimental data were obtained as
listed in Table S1. As shown in Figure S3, the kapp values for DMA are larger than
those for NIPAM, which is resulted from the polymerization feature of monomers.
4
And under the same conditions, the polymerizations mediated by CMP proceeded
more rapidly than that by mPEG-DMP. The slower polymerization rates mediated by
mPEG-DMP are likely a result of macromolecules as the leaving groups. It is also
noted that for both of CTAs there is no induction period due to the relatively shorter
half-life of KPS/NaAsc at 25°C.
6
PDMA
PEG-b-PDMA
PNIPAM
PEG-b-PNIPAM
ln([M])0/[M])
5
4
3
2
1
0
0
1
2
3
4
Time (h)
Figure S3. The kinetic plots for the aqueous RAFT polymerizations of DMA and
NIPAM using KPS/NaAsc as the redox initiators and CMP or mPEG-DMP as the
CTA at 25 °C. Molar feed ratio of [DMA]0 : [CTA]0 : [KPS]0 : [NaAsc]0 is 250 : 1 :
0.25 : 0.25, and the initial monomer concentration is 0.5 M.
As for RAFT polymerizations carried out at 25 °C, all the reactants are
homogeneously mixed and the induction period is hardly observed for four cases,
quite different from the phenomenon observed in cryopolymerization. As comparing
the kapp values at different temperatures, those for NIPAM with both CMP and
m-EPG-DMP as CTAs and that for DMA with CMP as CTA at -15°C reduce one
5
order of magnitude than those at 25°C. The lower temperature leads to larger decrease
of kapp values and the relatively longer half-life of KPS/NaAsc at -15°C causes the
presence of induction period.
Table S1. Comparison of kinetic parameters of RAFT polymerizations of DMA and
NIPAM with different CTAs at 25 °C.
monomer
apparent rate constant (kapp, s-1)
induction duration (Tind, min)
CMP
PEG-DMP
CMP
PEG-DMP
DMA
5.20 × 10-4
3.96 × 10-4
~0
~0
NIPAM
2.67 × 10-4
2.35 × 10-4
~0
~0
But for the polymerization of DMA mediated by mPEG-DMA, the kapp values at two
different temperatures are almost the same. The cryopolymerization of DMA with
mPEG-DMA proceeds more rapidly than others at -15°C. The higher concentration of
cryopolymerization caused by cryo-concentration accelerates the cryopolymerizations.
The influence of cryo-concentration for the polymerization of DMA mediated by
mPEG-DMA is very obvious. We attributed the results to the different physical
properties of these chemicals. Further investigation is needed to clarify this
phenomenon and disclose the mechanism of RAFT cryopolymerization.
6