Assembly of triblock copolymer brush at glass fiber/polystyrene interface and its effect on interfacial shear strength

To control the interfacial structure of glass fiber-reinforced composites, triblock copolymer coupling agents polystyrene-block-poly(n-butylacrylate)-block-poly(γ-methacryloxypropyltrimethoxysilane), (PS-b-PnBA-b-PMPS) were synthesized by atom transfer radical polymerization, then were chemically grafted on the glass fiber surfaces with a sufficiently high grafting density. When the grafted glass fibers are embedded in polystyrene (PS) matrix melt, copolymer brushes assemble at the interface of glass fiber/PS system to form the hemispherical domain morphology, where PnBA blocks form the inner core collapsing on fiber surface, while the outer layer PS blocks shield the PnBA blocks from PS homopolymer melt and entangle with the molecular chain of PS homopolymer. The influence of molecular architecture and organization of triblock copolymer coupling agents on the interfacial shear strength of glass fiber/PS system was investigated by means of Microbond Test. It is found that an increase in the PS block lengths is of advantage to the interfacial shear strength. A PnBA block length about the degree of polymerization (DPn) of 50 is desirable for the interfacial shear strength.