Double Reaction-induced Microphase Separation in Epoxy Resin Containing Polystyrene-block-poly(ε-caprolactone)-block-poly(n-butyl acrylate) ABC Triblock Copolymer

Abstract

Polystyrene-block-poly(ε-caprolactone)-block-poly(n-butyl acrylate) (PS-b-PCL-b-PBA) triblock copolymer was synthesized through the combination of atom transfer radical polymerization, copper-catalyzed Huisgen 1,3-dipolar cycloaddition and ring-opening polymerization. The PS-b-PCL-b-PBA ABC triblock copolymer was incorporated into epoxy to access the nanostructures in the thermoset. The microphase-separated morphology was investigated by means of atomic force microscopy (AFM), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA). It was found that depending on the concentration of the triblock copolymer in the thermosets several kinds of nanodomains were formed and they were arranged in lamellar lattice. The formation of the nanostructures was ascribed to the tandem reaction-induced microphase separation of PBA and PS blocks in the thermosetting blends. The investigation of the model binary thermosetting blends showed that the phase separation of PBA occurred at the conversion much lower than that of PS. It is proposed that the PBA nanophases were formed prior to the PS nanophases in the thermosetting blends and the microdomains of PBA subchains could behave as the template for the demixing of PS blocks. The coupling of the two-stage reactioninduced microphase separation exerted a profound impact on the formation of nanostructures in the epoxy thermosets containing the ABC triblock copolymer. Thermal analysis shows that with the formation of the nanostructures in the thermosets a part of poly(ε-caprolactone) subchains were demixed from epoxy matrix; the fractions of demixed PCL blocks have been estimated according to the T g -composition relation of the model binary blends of epoxy and PCL.

Nanostructured thermosets containing π-conjugated polymer nanophases: Morphology, dielectric and thermal conductive properties

“…The nanophases are not formed until the curing reaction occurs with the sufficiently high conversion of the precursors. In the past decade, there have been a great number of reports on the preparation of the nanostructured thermosets by using a variety of block copolymers via self-assembly or RIMPS approach [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. It is realized that thermosets can be significantly toughened via the formation of the nanostructures; the mechanisms of toughness improvement are attributable to the debonding of micelles (or vesicles) from thermosetting matrix, crack deflection or frictional interlocking in the thermosets displaying the terraced morphology [22].…”

Nanostructure Formation in Thermoset/Block Copolymer and Thermoset/Hyperbranched Polymer Blends

“…As a result, a higher cross-link density of the thermoset usually promises a higher T g when a hardener is fixed [31]. Meanwhile, different research groups [31,41,53,103] have reported an increased T g of their system with the introduction of different specific block copolymers, which is unexpected and not fully understood. This is attributed to the plasticization effect of miscible subchains in the copolymer that stretch out freely in the cured network [27,29,109].…”

Polymerization‐induced phase separation and resulting thermomechanical properties of thermosetting/reactive nonlinear polymer blends: A review

“…Fan et al 58 synthesized a PS-block-PCL-block-poly(n-butyl acrylate) (PBA) triblock copolymer to access nanostructures in ER. It was found that depending on the concentration of the triblock copolymer, several types of nanophases were formed in the thermosets.…”