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Synthesis and ring‐opening polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate; a comparison with the polymerization of 2,2‐dimethyltrimethylene carbonate
Author(s) -
Weilandt Karl D.,
Keul Helmut,
Höcker Hartwig
Publication year - 1996
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1996.021971128
Subject(s) - polymerization , chemistry , polymer chemistry , branching (polymer chemistry) , anionic addition polymerization , tetrahydrofuran , copolymer , alkyl , toluene , moiety , ring opening polymerization , polymer , solution polymerization , organic chemistry , solvent
The polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates (alkyl = methyl: AMTC, alkyl = ethyl: AETC) and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate (MMTC) in toluene with sec ‐butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(‐AETC) afford crystalline materials upon precipitation from solution while poly‐(AMTC) is amorphous; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2‐dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be k app DTC = 4 ċ 10 −3 s −1 , k app AETC = 4,28 ċ 10 −2 s −1 , and k app MMTC = 2,57 ċ 10 −2 s −1 . Studies of ring‐chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson‐Stockmayer the characteristic ratios of the polymers are C ∞ PDTC = 7,1, C ∞ PMMTC = 8,6, C ∞ PAETC = 9,9, and C ∞ PAMTC = 13,4.