Synthesis and characterization of block copolymers from 2-vinylnaphthalene by anionic polymerization

Abstract

The anionic polymerization of 2-vinylnaphthalene (2VN) has been studied in tetrahydrofuran (THF) at - 78°C and in toluene at 40°C. 2VN polymerization in THF, toluene, or toluene/THF (99:1 v/v) initiated by sec-butyllithium (sBuLi) indicates living characteristics, affording polymers with predefined molecular weights and narrow molecular weight distributions. Block copolymers of 2VN with methyl methyl methacrylate (MMA) and tert-butyl acrylate (tBA) have been synthesized successfully by sequential monomer addition in THF at -78°C initiated by aqn adduct of sBuLi-LiCl. The crossover propagation from poly(2-vinylnaphthyllithium) (P2VN) macroanions to MMA and tBA appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution of the resulting block copolymer is narrow (weight-average molecular/number-average molecular weight > 1.3). Block copolymeers with different chain lengths for the P2VN segment can easily be prepared by variations in the monomer ratios. The block copolymerization of 2VN with hexamethylcyclotrisiloxane also results in a block copolymer of P2VN and poly(dimethylsiloxane) (PDMS) contaminated with a significant amount of homo-PDMS. Poly(2VN-b-nBA) (where nBA is n-butyl acrylate) has also been prepared by the transesterification reaction of the poly(2VN-b-tBA) block copolymer. Size exclusion chromatography, Fourier transform infrared, and 1H NMR measurements indicate that the resulting polymers have the required architecture. The corresponding amphiphilic block copolymer of poly(2VN-b-AA) (where AA is acrylic acid) has been synthesized by acidic hydrolysis of the ester group of tert-butyl from the poly(2VN-b-tBA) copolymer.