Abstract
The chemical modification (namely the epoxidation) of a star shaped block copolymer (BCP) based on polystyrene (PS) and polybutadiene (PB) and its effect on structural and mechanical properties of the polymer were investigated. Epoxidation degrees of 37 mol%, 58 mol%, and 82 mol% were achieved by the reaction of the copolymer with meta-chloroperoxy benzoic acid (m-CPBA) under controlled conditions. The BCP structure was found to change from lamellae-like to mixed-type morphologies for intermediate epoxidation level while leading to quite ordered cylindrical structures for the higher level of chemical modification. As a consequence, the glass transition temperature (Tg) of the soft PB component of the BCP shifted towards significantly higher temperature. A clear increase in tensile modulus and tensile strength with a moderate decrease in elongation at break was observed. The epoxidized BCPs are suitable as reactive templates for the fabrication of nanostructured thermosetting resins.
Highlights
Styrene/butadiene (SB) block copolymers (BCPs) represent a group of advanced materials with a wide range of applications [1,2], in which the polymers synergistically combine the hard and rigid thermoplastic nature of polystyrene (PS) with the soft and flexible segments of polybutadiene (PB)
In order to enhance their compatibility with the epoxy system, the BCPs can be chemically modified by epoxidation of the PB block
The sections were transferred to a carbon grid and the PB-rich phase of the BCP morphology was selectively stained with osmium tetroxide
Summary
Styrene/butadiene (SB) block copolymers (BCPs) represent a group of advanced materials with a wide range of applications [1,2], in which the polymers synergistically combine the hard and rigid thermoplastic nature of polystyrene (PS) with the soft and flexible segments of polybutadiene (PB). Relative chemical composition, and nature of monomers the properties of the BCPs can be adjusted over a wide range covering a material portfolio from thermoplastic elastomers [8,9] to toughened thermoplastics [10,11,12,13,14,15] In addition to their use as components in medical equipment, household technology, and automotive industry or the information technology (IT) sector, SB-based BCPs are used, for example, in adhesives and sealants and asphalt formulations [16,17,18,19]. One of the common strategies to epoxidize diene group containing polymers involves the in situ formation of peracids through the reaction between formic acid and hydrogen peroxide [23,24,25,26,27]. The study attempts to adjust variable epoxidation degrees and to characterize its impact on structural and mechanical behavior of the polymer
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