TY - JOUR
T1 - Precise Control of Molecular Weight and Stereospecificity in Lewis Pair Polymerization of Semifluorinated Methacrylates
T2 - Mechanistic Studies and Stereocomplex Formation
AU - Wang, Xing
AU - Hong, Miao
N1 - Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/6/23
Y1 - 2020/6/23
N2 - Unlike the other common polar conjugated monomers, the efficient and precise polymerization of semifluorinated methacrylates (SFMAs) by conventional anionic or coordination polymerization has remained an unmet challenge, despite the unique and intriguing characteristics of the resulting polymers. This contribution reports the first Lewis pair polymerization (LPP) of SFMAs that provides a viable and effective strategy for the efficient synthesis of semifluorinated polymethacrylates (SFPMAs) with precise control over molecular weight and stereospecificity. Among Lewis pair (LP) catalysts based on N-heterocyclic carbene (NHC) Lewis bases (LBs) and group 13 Lewis acids (LAs), a strongly nucleophilic 1,3-di-tert-butylimidazolin-2-ylidene (ItBu) LB and a strongly Lewis acidic and sterically encumbered methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) [MeAl(BHT)2] LA have stood out as the best LP catalyst in all aspects for SFMA LPP. Even at an exceptionally large excess of SFMA (e.g., 4500 equiv), quantitative monomer conversion can be achieved by this LP at room temperature within 60-180 min, affording ultrahigh-molecular-weight SFPMAs with very low dispersities (Mn up to 1300 kg/mol, Ä = 1.01-1.10). For the typical SFMAs of trifluoroethyl methacrylate (TFEMA) and hexafluorobutyl methacrylate (HFBMA), living characteristics of their LPPs have been unequivocally established, and a fundamental understanding of this living feature has also been gained by the mechanistic studies. Highly syndioregular PTFEMA, with a high syndiotacticity of [rr] up to 92.0% and a low Ä of 1.16, can be produced at low temperature, which readily forms a stereocomplex with isotactic poly(methyl methacrylate), thus affording a robust fluorinated-contained crystalline material with a high melting temperature up to 175 C.
AB - Unlike the other common polar conjugated monomers, the efficient and precise polymerization of semifluorinated methacrylates (SFMAs) by conventional anionic or coordination polymerization has remained an unmet challenge, despite the unique and intriguing characteristics of the resulting polymers. This contribution reports the first Lewis pair polymerization (LPP) of SFMAs that provides a viable and effective strategy for the efficient synthesis of semifluorinated polymethacrylates (SFPMAs) with precise control over molecular weight and stereospecificity. Among Lewis pair (LP) catalysts based on N-heterocyclic carbene (NHC) Lewis bases (LBs) and group 13 Lewis acids (LAs), a strongly nucleophilic 1,3-di-tert-butylimidazolin-2-ylidene (ItBu) LB and a strongly Lewis acidic and sterically encumbered methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) [MeAl(BHT)2] LA have stood out as the best LP catalyst in all aspects for SFMA LPP. Even at an exceptionally large excess of SFMA (e.g., 4500 equiv), quantitative monomer conversion can be achieved by this LP at room temperature within 60-180 min, affording ultrahigh-molecular-weight SFPMAs with very low dispersities (Mn up to 1300 kg/mol, Ä = 1.01-1.10). For the typical SFMAs of trifluoroethyl methacrylate (TFEMA) and hexafluorobutyl methacrylate (HFBMA), living characteristics of their LPPs have been unequivocally established, and a fundamental understanding of this living feature has also been gained by the mechanistic studies. Highly syndioregular PTFEMA, with a high syndiotacticity of [rr] up to 92.0% and a low Ä of 1.16, can be produced at low temperature, which readily forms a stereocomplex with isotactic poly(methyl methacrylate), thus affording a robust fluorinated-contained crystalline material with a high melting temperature up to 175 C.
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U2 - 10.1021/acs.macromol.0c00553
DO - 10.1021/acs.macromol.0c00553
M3 - Article
AN - SCOPUS:85084584320
SN - 0024-9297
VL - 53
SP - 4659
EP - 4669
JO - Macromolecules
JF - Macromolecules
IS - 12
ER -