Poly(acrylate-b-styrene-b-isobutylene-b-styrene-bacrylate) block copolymers via carbocationic and atom transfer radical polymerizations

A series of polyacrylate-polystyrene-polyisobutylene-polystyrene-polyacrylate (X-PS-PIB-PS-X) pentablock terpolymers (X = poly( methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly( methyl methacrylate) ( PMMA)) was prepared from poly (styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers (BCPs) using either a Cu(I) Cl/1,1,4,7,7-pentamethyldiethylenetriamine(PMDETA) or Cu(I) Cl/tris[2( dimethylamino) ethyl] amine (Me6TREN) catalyst system. The PS-PIB-PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization ( ATRP) of methyl acrylate ( MA), n-butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu( I) Cl/PMDETA or Cu( I) Cl/ Me6TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. H-1-NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS-PIB-PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material

Molecular Weight Effects on the Mechanical Properties of Novel Epoxy Thermoplastics

A series of epoxy thermoplastics (ETPs) with varying molecular weights were synthesized from a difunctional diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin and an aromatic secondary diamine. The materials possessed glass transition temperatures varying between 73.61 and 85.36 degrees C. The ETP series was characterized for fracture toughness, flexural, and compression properties. In general, fracture properties increased with increasing molecular weight and yet were consistently shown to decrease when higher molecular weight values were the result of increased branching. Flexural ultimate strength and strain-at-break increased with increasing molecular weight while flexural modulus decreased to a plateau. Compression properties were relatively unaffected by changes in molecular weight over the range of materials synthesized