Influence of PS‐b‐PEO diblock copolymers on the compatibility of syndiotactic polystyrene modified epoxy blends

Abstract

Homogeneous solutions of syndiotactic polystyrene (sPS) in diglycidylether of bisphenol A (DGEBA), containing 2.5, 5 and 7.5 wt % of thermoplastic with or without 0.5 and 1 wt % of poly(styrene-b-ethylene oxide) (PS-b-PEO) block copolymer, were polymerized using a stoichiometric amount of an aromatic amine hardener, 4,4Ј-methylene bis (3-chloro-2,6-diethylaniline) (MCDEA). The dynamic-mechanical properties and morphological changes of sPS-(DGEBA/MCDEA) compatibilized with different amount of PS-b-PEO have been investigated in this paper. The addition of the block copolymer produced significant changes in the morphologies generated. The size of the dispersed spherical sPS spherulites does not change significantly, but less spherulites of sPS appeared upon network formation in the systems with compatibilizer, what means that addition of compatibilizer in this system delayed crystallization of sPS in sPS-(DGEBA/MCDEA) systems and change phase separation mechanism from crystallizationinduced phase separation (CIPS) and reaction-induced phase separation (RIPS) almost only to RIPS. Moreover, PS-b-PEO with higher molecular weight of PS block seems to be a more effective compatibilizer than one with lower molecular weight of PS block.

Nanoindentation study of interphases in epoxy/amine thermosetting systems modified with thermoplastics

“…Different morphologies on epoxy/amine and thermoplastic phases can be appreciated, being rougher the thermoplastic surface, due to the different cutting behavior during sample preparation. It is well known that the epoxy/amine-aPS mixture, with the amine MCDEA, generates reaction induced phase separation through curing of the epoxy matrix [49][50][51]. Systems with semicrystalline polymers show the initial contact border without any signs of reaction induced phase separation, so, a more detailed study of diffusion was carried out on the system with aPS by performing larger scale AFM scans.…”

Liquid crystal alignment in electro-responsive nanostructured thermosetting materials based on block copolymer dispersed liquid crystal

“…Recently, based on work done by Hoppe et al [33,34] and our previous papers [15][16][17][18][19][20][35][36][37][38][39][40], a new strategy of preparation of multifunctional thermo-responsive nanostructured thermosetting systems modified with block copolymer dispersed liquid crystals has been published by us [41,42]. The present contribution reports the possibility of obtaining a well-defined nanostructured thermosetting system based on this strategy.…”

“…The number-average molecular weight for PS and PEO blocks is 58 600 g mol −1 and 31 000 g mol −1 , respectively, the polydispersity index for this copolymer being 1.03. Additionally, the low molecular weight nematic liquid crystal, 4 -(hexyl)-4-biphenyl carbonitrile [35], supplied by Sigma-Aldrich, was used as a modifier without further purification. This liquid crystal exhibits a nematic-isotropic (T N -T I ) transition at about 34 • C and a crystal-nematic (T C -T N ) transition at about 24 • C, as revealed by differential scanning calorimetry (DSC) and optical microscopy (OM) [35,41,40].…”

Multifunctional Thermally Reversible Nanostructured Thermosetting Materials Based on Block Copolymers Dispersed Liquid Crystal

“…[24][25][26] Whereas several studies have shown a new family of polymer-dispersed LCs, [27][28][29][30] where the LC is dispersed in a thermoplastic/thermoset matrix, to the best of our knowledge, the possibility of using block copolymers as modifiers in thermoset systems and their ability to act as thermally reversible nanostructured thermosetting materials have not been reported yet. Taking into account the work done by Hoppe et al [27,28] and our previous papers, [10][11][12][29][30][31][32][33] the main aim of the present contribution is to investigate the possibility of obtaining novel meso/nanostructured thermosetting materials, which can be thermally reversible based on a thermosetting system modified with a block copolymer and a nematic lowmolecular-weight LC. Bisphenol A-type epoxy resin, modified with an amphiphilic block copolymer based on polystyrene and poly(ethylene oxide) (PSEO) and a low-molecular-weight nematic LC, 4 0 -(hexyl)-4-biphenylcarbonitrile (HBC), has been cured with a stoichiometric amount of an aromatic amine hardener, m-xylylenediamine (MXDA).…”