292
M. Hong
of 1.19 ([VBMA] 0 :[LB] 0 :[LA] 0 = 200:1:2, TOF = 1200 h
−1 , M n = 39.1 kg/mol).
When switching to EtAl(BHT) 2 LA and NHO-8 (Scheme 8.5b) LB to construct sterically more demanding LP catalysts [MeAl(BHT) 2 /NHO-8, et al. (BHT) 2 /NHO-8],
near quantitative I
* values (93–102%) and relatively low Ð values of the resulting
PVBMAs (1.23–1.27) were maintained, but the polymerization activity decreased
(TOF = 120–600 h
−1 ).
In the same year, Zhang et al. utilized MeAl(BHT) 2 /NHO-1 and
MeAl(BHT) 2 /NHO-3 FLPs as well as MeAl(BHT) 2 /NHO-7 CLA (Schemes 8.2
and 8.4) for the successful chemoselective polymerization of AMA and VMA
(Scheme 8.1d) [42]. The living characteristics of MeAl(BHT) 2 /NHO-1 FLPmediated polymerizations of AMA and VMA were clearly verified. For all
[M] 0 :[NHO-1] 0 :[MeAl(BHT) 2 ] 0 ratios from 200:1:2 to 800:1:2, monomers can be
fully polymerized into the corresponding polymers (TOF = 800–6000 h
−1 ) with
predicted M n s, relatively low Ð values (1.10–1.39), and high to near quantitative I
*
values (81–103%). The stoichiometric reaction of NHO-1 with MeAl(BHT) 2 ·AMA
indicated that the formed zwitterionic active species gradually transformed into
a deactivated intermediate through the Claisen rearrangement (Scheme 8.5c).
Therefore, during the sequential block copolymerizations, the subsequent batch of
comonomers after AMA block must be added in time to avoid the formation of
this deactivated intermediate. Accordingly, the well-defined diblock copolymers
(PMMA-b-PAMA, PAMA-b-PMMA and PAMA-b-PVMA) and triblock copolymers
(PMMA-b-PAMA-b-PMMA, PAMA-b-PMMA-b-PAMA and PAMA-b-PVMA-bPAMA), as well as random PMMA-co-PAMA copolymer bearing pendant vinyl
groups, can be successfully prepared. Different from MeAl(BHT) 2 /NHO-1 FLP
catalyst, decreasing the catalyst loading ([AMA] 0 :[LB] 0 :[LA] 0 = 800:1:2) in the
polymerizations by MeAl(BHT) 2 /NHO-3 FLP and MeAl(BHT) 2 /NHO-7 CLA
broadened the dispersities of the resultant polymers (Ð: 1.78–1.81).
To overcome the issue of poor control that is generally encountered in LPP of
acrylamides, [26, 30, 38, 39, 47] in 2019, Zhang et al. investigated LPP of DMAA at
RT catalyzed by NHO-based (Scheme 8.2) LPs using a series of organoaluminums
as LAs [48], including Al(C 6 F 5 ) 3 (100) > AlPh 3 ·OEt 2 (88) ≈ MeAl(BHT) 2 (86) >
AlMe 3 (71) ≈ AlEt 3 (70) = Al
i Bu 3 (70), the Lewis acidities of which were measured
by the Gutmann-Beckett method [49, 50]. Fixing a [DMAA] 0 :[LB] 0 :[LA] 0 ratio of
800:1:2, when weakly acidic AlMe 3 or AlEt 3 was employed as an LA to pair with
NHO-1 LB, the polymerization occurred rapidly with quantitative monomer conversion accomplished within 30 s (TOF = 96000 h
−1 , M n = 281–303 kg/mol, Ð =
1.13), but I
* values of these polymerizations were low rather low (26–28%) and backbiting chain termination was observed in AlMe 3 /NHO-1-mediated polymerization.
Switching to a sterically more demanding Al
i Bu 3 , a PDMAA with a bimodal distribution was produced, which should be caused by Al
i Bu 3 -initiated background polymerization. Remarkably, CLAs comprising relatively stronger acidic AlPh 3 ·OEt 2 LA
and NHO-1–4 LB not only exhibited exceedingly high activity but also showed living
characterization toward DMAA LPP (TOF = 96000 h
−1 , M n = 104–116 kg/mol,
Ð = 1.06–1.07, I
*
= 69–76%). Good controllability can also be extended to N,Ndiethylacrylamide (TOF = 96000 h
−1 , M n = 90 kg/mol, Ð = 1.12, I
*
= 113%), and
M. Hong
of 1.19 ([VBMA] 0 :[LB] 0 :[LA] 0 = 200:1:2, TOF = 1200 h
−1 , M n = 39.1 kg/mol).
When switching to EtAl(BHT) 2 LA and NHO-8 (Scheme 8.5b) LB to construct sterically more demanding LP catalysts [MeAl(BHT) 2 /NHO-8, et al. (BHT) 2 /NHO-8],
near quantitative I
* values (93–102%) and relatively low Ð values of the resulting
PVBMAs (1.23–1.27) were maintained, but the polymerization activity decreased
(TOF = 120–600 h
−1 ).
In the same year, Zhang et al. utilized MeAl(BHT) 2 /NHO-1 and
MeAl(BHT) 2 /NHO-3 FLPs as well as MeAl(BHT) 2 /NHO-7 CLA (Schemes 8.2
and 8.4) for the successful chemoselective polymerization of AMA and VMA
(Scheme 8.1d) [42]. The living characteristics of MeAl(BHT) 2 /NHO-1 FLPmediated polymerizations of AMA and VMA were clearly verified. For all
[M] 0 :[NHO-1] 0 :[MeAl(BHT) 2 ] 0 ratios from 200:1:2 to 800:1:2, monomers can be
fully polymerized into the corresponding polymers (TOF = 800–6000 h
−1 ) with
predicted M n s, relatively low Ð values (1.10–1.39), and high to near quantitative I
*
values (81–103%). The stoichiometric reaction of NHO-1 with MeAl(BHT) 2 ·AMA
indicated that the formed zwitterionic active species gradually transformed into
a deactivated intermediate through the Claisen rearrangement (Scheme 8.5c).
Therefore, during the sequential block copolymerizations, the subsequent batch of
comonomers after AMA block must be added in time to avoid the formation of
this deactivated intermediate. Accordingly, the well-defined diblock copolymers
(PMMA-b-PAMA, PAMA-b-PMMA and PAMA-b-PVMA) and triblock copolymers
(PMMA-b-PAMA-b-PMMA, PAMA-b-PMMA-b-PAMA and PAMA-b-PVMA-bPAMA), as well as random PMMA-co-PAMA copolymer bearing pendant vinyl
groups, can be successfully prepared. Different from MeAl(BHT) 2 /NHO-1 FLP
catalyst, decreasing the catalyst loading ([AMA] 0 :[LB] 0 :[LA] 0 = 800:1:2) in the
polymerizations by MeAl(BHT) 2 /NHO-3 FLP and MeAl(BHT) 2 /NHO-7 CLA
broadened the dispersities of the resultant polymers (Ð: 1.78–1.81).
To overcome the issue of poor control that is generally encountered in LPP of
acrylamides, [26, 30, 38, 39, 47] in 2019, Zhang et al. investigated LPP of DMAA at
RT catalyzed by NHO-based (Scheme 8.2) LPs using a series of organoaluminums
as LAs [48], including Al(C 6 F 5 ) 3 (100) > AlPh 3 ·OEt 2 (88) ≈ MeAl(BHT) 2 (86) >
AlMe 3 (71) ≈ AlEt 3 (70) = Al
i Bu 3 (70), the Lewis acidities of which were measured
by the Gutmann-Beckett method [49, 50]. Fixing a [DMAA] 0 :[LB] 0 :[LA] 0 ratio of
800:1:2, when weakly acidic AlMe 3 or AlEt 3 was employed as an LA to pair with
NHO-1 LB, the polymerization occurred rapidly with quantitative monomer conversion accomplished within 30 s (TOF = 96000 h
−1 , M n = 281–303 kg/mol, Ð =
1.13), but I
* values of these polymerizations were low rather low (26–28%) and backbiting chain termination was observed in AlMe 3 /NHO-1-mediated polymerization.
Switching to a sterically more demanding Al
i Bu 3 , a PDMAA with a bimodal distribution was produced, which should be caused by Al
i Bu 3 -initiated background polymerization. Remarkably, CLAs comprising relatively stronger acidic AlPh 3 ·OEt 2 LA
and NHO-1–4 LB not only exhibited exceedingly high activity but also showed living
characterization toward DMAA LPP (TOF = 96000 h
−1 , M n = 104–116 kg/mol,
Ð = 1.06–1.07, I
*
= 69–76%). Good controllability can also be extended to N,Ndiethylacrylamide (TOF = 96000 h
−1 , M n = 90 kg/mol, Ð = 1.12, I
*
= 113%), and