Block Copolymer Concentration Gradient and Solvent Effects on Nanostructuring of Thin Epoxy Coatings Modified with Epoxidized Styrene–Butadiene–Styrene Block Copolymers

Abstract

The gradient on block copolymer concentration through film thickness as well as the effects of casting solvents used on the nanostructuring of a thermosetting epoxy coating modified with an epoxidized poly­(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer was studied by means of atomic force microscopy and attenuated total reflectance infrared spectroscopy. Thin coating films based on a commercial epoxy– amine formulation consisting of diglycidyl ether of bisphenol A and a low-temperature fast curing amine were modified with several amounts of epoxidized SBS triblock copolymer. Toluene and a mixture of tetrahydrofuran and N,N-dimethylformamide were used as casting solvents. With epoxidation degrees higher than 45 mol % of polybutadiene block nanostructuring was achieved. Fast curing rate of the epoxy/amine system and the comparatively slow evaporation rate of the casting solvent led to a gradient of morphologies through the film cross section owing to the coalescence of small micelles into larger micellar domains in the case of low block copolymer content. For these reasons, different morphologies were also obtained in the midtransverse section of a film with variable thickness. Finally, pseudolamellar nanostructure at high copolymer contents was achieved as confirmed by parallel and perpendicular cuttings to the air/polymer interface.

Nanostructured thermosetting epoxy systems modified with poly(isoprene‐b‐methyl metacrylate) diblock copolymer and polyisoprene‐grafted carbon nanotubes

“…The spherical‐shaped micelle nanodomains were ascribed to PI chains. It has to be noted that the number and the size of spherical nanodomains, and consequently the volume fraction of the separated phase increased with increasing PI‐ b ‐PMMA content25 but the nanostructure did not shift from spherical micelles to any other morphology. This fact was confirmed by analytical treatment of images.…”

Engineering superior toughness in commercially viable block copolymer modified epoxy resin

“…In this case, both the thermodynamic interactions between components and the reaction kinetics of the reactive block with the epoxy resin and of cross‐linking of the epoxy itself, strongly affect the formation of nanophases. The control of reaction induced morphologies in bulk epoxy thermosets or even in thin films arouses continuous interest to‐date. Those morphologies were usually obtained at relatively high block copolymer concentrations (> 10 wt %), and the authors did not report the influence of these interesting microstructures on epoxy mechanical properties.…”

Preparation and characterization of polarity-modulated SIS-based hot-melt pressure-sensitive adhesives

“…These methods have been used to introduce polar functional groups in the styrene or diene blocks of the styrenic block copolymers. [12,[21][22][23][24][25][26][27] Among these methods, the epoxidation procedures are utilized to incorporate epoxide groups into the diene blocks of the copolymers, in which some oxidants, such as metal catalyzed/hydrogen peroxide, dimethyldioxirane, meta-chloroperbenzoic acid, and in situ per-formic acid, have been adopted. [22,[28][29][30] To synthesize templates for nanostructured thermosets, metal catalyzed/hydrogen peroxide, dimethyldioxirane, and meta-chloroperbenzoic acid have been utilized to epoxidize SIS or SBS copolymers with high epoxidation degrees (>60 mol%).…”

“…[12,[21][22][23][24][25][26][27] Among these methods, the epoxidation procedures are utilized to incorporate epoxide groups into the diene blocks of the copolymers, in which some oxidants, such as metal catalyzed/hydrogen peroxide, dimethyldioxirane, meta-chloroperbenzoic acid, and in situ per-formic acid, have been adopted. [22,[28][29][30] To synthesize templates for nanostructured thermosets, metal catalyzed/hydrogen peroxide, dimethyldioxirane, and meta-chloroperbenzoic acid have been utilized to epoxidize SIS or SBS copolymers with high epoxidation degrees (>60 mol%). [22,23,29,31,32] But, they are seldom used to polarize the HMPSAs because most of them can produce a significant amount of side reactions, such as ring opening and cross-linking.…”

“…[22,[28][29][30] To synthesize templates for nanostructured thermosets, metal catalyzed/hydrogen peroxide, dimethyldioxirane, and meta-chloroperbenzoic acid have been utilized to epoxidize SIS or SBS copolymers with high epoxidation degrees (>60 mol%). [22,23,29,31,32] But, they are seldom used to polarize the HMPSAs because most of them can produce a significant amount of side reactions, such as ring opening and cross-linking. Furthermore, high epoxidation degrees may shift glass transition temperature of diene phase outside the HMPSAs window.…”