Synthesis of Epoxy-Functional Microspheres by Cationic Suspension Photopolymerization

Abstract

This article describes the development of a novel rapid one-step cationic suspension photopolymerization method for the synthesis of epoxy-functional polymeric microspheres ranging in size from 50 nm to 100 μm. Multifunctional silicon-containing epoxy monomers and oligomers were photopolymerized to produce microspheres in both in aqueous and nonaqueous suspensions using a variety of cationic photoinitiators. Various solvents with controlled polarities were employed to produce macroporous particles. The effects of a variety of experimental and compositional variables on the particle diameter, size distribution, and epoxy content of the microspheres were examined. Among the parameters that were evaluated were the initiator composition and concentration, agitation method, UV irradiation time, viscosities of both the monomer and suspending medium, and type of porogen used. Following synthesis, the microspheres were characterized by SEM microscopy and by titration to determine the epoxy-functional group content. Microspheres that were subjected to pyrolysis at 700 °C retained their macrostructure despite undergoing a 60% weight loss.

Synthesis and modification of epoxy‐ and hydroxy‐functional microspheres

“…10 The apparatus shown in Figure 1 consists of a cylindrical quartz reaction vessel (7.6 cm in diam by 12.7 cm) and an overhead stirrer (IKA, Inc. Wilmington, NC) equipped with a 5 cm diam three-paddle stainless-steel stirrer obtained from Fisher Scientific (Burr Ridge, IL) and a ultrasonication wand (13 cm) powered by a Vibra-Cell 750 W ultrasonicator (VCX 750, Vibracell Sonics, Newton, CT). The UV irradiation was supplied by a Hanovia 679A36 medium pressure mercury are lamp (Hanovia Ltd, Slough, UK) equipped with a 200 W power supply.…”

“…Recently, 10 we have reported that highly functional microspheres bearing epoxy groups can be obtained directly by the cationic suspension photopolymerization of multifunctional epoxy monomers. The general concept is depicted in Scheme 1.…”

Photo‐Initiated Dispersion Polymerization of Copolymer Microspheres in a Closed System: Poly(MMA‐co‐MAA)

“…It can generally be carried out more rapidly and easily than the corresponding thermal processes, and several groups have obtained some good results. In these studies, dispersion, [2] aerosol, [23,24] cationic suspension, [25] and emulsion [26,27] photopolymerizations had been used to prepare PMMA, multiacrylate, and epoxy-functionalized microspheres, respectively. Either high-power UV lamps or complicated operations must be employed in these reports and none had dealed with preparations of copolymer microspheres.…”

Synthesis of polymeric microcapsules by interfacial-suspension cationic photopolymerisation of divinyl ether monomer in aqueous suspension

“…10 This synthetic method used a cationic photopolymerisation process, as well as conventional cationic vinyl and ring-opening polymerization, to realise a reaction that is well-known to be water sensitive. 11 Vinyl ethers are widely used in polymerisations for their ability to form networks with high efficiency for applications such as coatings, lithography etc. 9 Sangermano et.…”

“…al. 11 report the synthesis of epoxy functionalized microspheres by cationic photopolymerization in aqueous conditions. It is important to underline that the typical water suspension polymerization comprises hydrophobic monomers, in which droplets (oil phase) are emulsified with surfactants in a continuous phase of water.…”