Synthesis, Thermodynamics and Processing of Block Copolymer Based Nanocomposites

摘要

Two sets of model diblock copolymers were synthesized using anionic polymerization and heterogeneous catalytic hydrogenation: Poly(ethylene)- poly(ethylenepropylene) (PE-PEP) and poly(ethyleneoxide)-poly(alkane) (PEO-PA) where PA is PEP or poly(ethylethylene) (PEE). Blends of PE-PEP with the respective PE and PEP homopolymers were shown to form a bicontinuous microemulsion using small-angle neutron scattering (SANS) and transmission electronmicroscopy (TEM) measurements. Thermoset resins composed of bisphenol-A- co-epichorohydrin (BA348) and methylene dianiline (MDA) hardener have been modified through the addition of PEO-PEP diblock copolymers. Self-assembly of the diblocks leads to ordered lamellar (L), cylindrical (C), bicontinuous gyroid (G), and spherical (S) microdomains as evidenced by SAXS and SANS. Thermally induced curing results in clear, uniform nanocomposites with prescribed morphologies as revealed by TEM. Crosslinking inking was found to induce local segregation of PEO from the epoxy without any evidence of macrophase separation. In the limit of low block copolymer concentrations a monodisperse microemulsion is obtained with domain dimensions that scale with molecular weight. Compact tensile fracture tests revealed a 30% improvement in K(1C) with the addition of just 5% block copolymer. These findings constitute unprecedented control over the morphology of thermoset plastic materials.