Formation and Confined Crystallization of Polyethylene Nanophases in Epoxy Thermosets

Abstract

In this contribution, we reported the investigation of the formation and confined crystallization behavior of polyethylene nanophases in epoxy thermosets. The nanostructured epoxy thermosets were prepared by the use of a poly(ε-caprolactone)-block-polyethylene-block-poly(ε-caprolactone) (PCL-b-PE-b-PCL) triblock copolymer. The crystalline midblock (viz. PE) of the triblock copolymer was prepared from an α,ω-diacetoxy-terminated polycyclooctadiene with the molecular weight as high as M n = 11,000, which was synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctadiene catalyzed by Grubbs second generation catalyst. The formation of PE nanophases in epoxy thermosets was evidenced with transmission electronic microscopy (TEM), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA). It was found that in the nanostructured thermosets, the spherical nanophases of PE with the size of 20–30 nm in diameter were dispersed into the continuous epoxy matrices. Wide angle X-ray diffraction (XRD) showed that the formation of PE nanophases did not alter the structure of PE crystals. The investigations of isothermal and nonisothermal crystallization kinetics showed that the crystallization of PE in the nanostructured thermosets was in a confined manner and the confinement has been interpreted on the basis of nanoscaled space, interdomain connectivity, and the cross-linked structures of epoxy matrices.

Enhancement of dielectric constants of epoxy thermosets via a fine dispersion of barium titanate nanoparticles

“…The results of both DSC and DMTA indicated that the PCL chains grafted onto the surfaces of the BT NPs were miscible with the epoxy matrices. The miscibility of the PCL chains with epoxy networks was attributed to the formation of intermolecular hydrogen‐bonding interactions between the carbonyl groups of the PCL chains and the hydroxyl groups of the epoxy networks …”

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].…”

Polyblend Nanocomposites

“…Wide angle (WA) XRD showed that the formation of PE nanophases didn't alter the structure of the crystals (72). 652 Feldman EP/MMT prepared through solid state reaction was melt-processed with PA6.…”