Supporting information
1. Affiliation of 1H NMR spectrum for the polymer
The radical addition-coupling reaction must be as the major route in the
polymerization, or Xn,GPC could not be as high in Table 2, and gels could not be
obtained.
①For acrylate-typed carbon radical, disproportionation, coupling termination reaction
and chain transfer reaction may occur, we made an in-depth study in this section.
From the 1H NMR spectra of the products it was found a very small amount of
coupling reaction units in the polymers (Figure 1), but it could be negligible in the
main reactions of the polymerization. There was not found any evidence of
disproportionation reaction of the carbon radical at δ=5.5-6.5. The chain transfer
reaction of alkoxy amine radical can not be ignored if the coupling reaction between
carbon radical and alkoxy amine radical was restrained due to steric effect, as shown
in Figure 2.
Figure 1. Evidence of self coupling reaction of carbon radicals in polymerization in the
1
H NMR spectra. Reaction condition: rA = 2nA1/(3nMNP) = 1, cA1 = 0.008M, VTHF = 4 mL,
nCu: nPMDETA=1: 1, 25 oC, 15h. nCu = x×3nA1, x = 48% (a) and 52% (b), respectively.
② Trace amount of NOH in the end
The 1H NMR spectrum of the polymer after deuterium exchange is shown in Figure 2.
The disappeared peak indicated that reactive hydrogen existed in the polymer. To
exclude the possibility of NH and SH in the monomer or product, and end alkoxy
amine radical may occur hydrogen abstraction reaction to generate NOH structure
[1-4] if the coupling reaction between carbon radical and alkoxy amine radical was
restrained due to steric effect, NOH structure was confirmed.
Figure 2. Comparison of the 1H NMR spectra of the polymer prepared by A1 and MNP
before (above) and after (below) deuterium exchange.
③Cyclic structure detected by ESI-MS
Figure 3. (a) ESI-MS spectrum of the product (nA1: nMNP: nCu: nPMDETA = 1: 3: 15: 10,
[A1] = 0.001 M, VTHF = 80 ml, 25 °C, 40 h); (b) The right pictures are simplified
structures for cyclic oligomers.
As shown in Figure 3(a), the ESI-MS spectrum of the polymer exhibites peaks at 882.3
and 1741.5, which were assigned to cyclic oligomers with structures shown in Figure
3(b), identified as the sodium adduct ions. The result reflected unavoidable cyclic
reactions between polyfunctional groups. The left model represented two cycles, and
the right model represented three cycles.
2. Selective degradation of ester group in the polymer.
Degradation of ester group in the polymer could occur at a certain concentration of
KOH/methanol without jeopardizing NO–C, as shown in Scheme 1. The R–OC(O)–R’
structure in polymer could be changed to R–OH and CH3OC(O)–R’, while NO–C in
polymer was conserved.
Scheme 1. Degradation mechanism of hyperbranched polystyrene.
To determine the appropriate degradation condition, we established two model
polymers, dimethyl 2,9-dibromodecanedioate-alt-MNP and 3-arm P(tert-butyl
acrylate), which was synthesized by the tribromide and tert-butyl acrylate via ATRP.
The ester appeared at the side chain of dimethyl 2,9-dibromodecanedioate-alt-MNP
but at the backbone of the 3-arm PtBA. If the ester is broken, the Mn,GPC of dimethyl
2,9-dibromodecanedioate- alt-MNP is similar with the original value, but Mn,GPC of
3-arm PtBA will reduce to 1/3 of the original value. Under the proper condition,
polymers were degraded. The results could be seen in Figure 4 and Table 1.
Fig. 4 Comparisons of GPC curves of two model polymers before and after ester
exchange degradations in certain condition (left, the employed polymer is
MNP-alt-dimethyl 2,9-dibromodecanedioate; right, the employed polymer is 3-arm
PtBA).
Table 1.
Results of degradation of ester group in the polymers.
Run
Mn,GPC (g/mol)
PDI
Time (h)
MNP-alt-dimethyl
13200
1.78
0
2,9-dibromodecanedioate
After methanolysis a
14800
1.50
21
3-arm PtBA
9800
1.07
0
a
After methanolysis
3700
1.22
15
a
The cleavage test condition: 25 mg polymer, 2 ml of methanol and 3 ml of THF, 0.2
ml of 0.1M KOH/methanol solvent were added to a 10 ml round-bottom flask, sealed
by stopper, kept at 50 °C.
The NO–C in the linear polymer could be conserved after ester exchange reaction for
21 h, the Mn,GPC values were similar to each other before and after degradation. But
R–C(O)O-R’ was changed into R–C(O)O-CH3 because the Mn,GPC of the 3-arm PtBA
reduced to 1/3 of the original value in Table 1. However, NO–C would be destroyed if
the KOH concentration was above 0.1M, and the process took a much longer time if
the concentration was below this threshold.
References
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