Molecular mass control in methacrylic copolymer latexes containing glycidyl methacrylate

Abstract

SYNOPSISResults are presented on the preparation and characterization of batch emulsion copolymers of butyl methacrylate and glycidyl methacrylate (GMA). The two main problems occurring during an emulsion copolymerization with GMA are partial hydrolysis of the epoxy groups and internal crosslinking of the latex particles formed. The influence of chain transfer agents (CTA) on the degree of crosslinking was investigated. Furthermore, the effect of reaction temperature and the addition of methacrylic acid on the sol/gel content of the polymer formed and on the rate of epoxy hydrolysis were investigated. It was found that lowering the reaction temperature did not increase the sol content; however, it significantly decreased the extent of hydrolysis. The addition of a CTA (especially CBr,) increased the sol content of the polymer, and good control over the molecular mass was achieved. The addition of methacrylic acid showed that this monomer can be used without any complications with respect to the control of the sol content of the polymer formed. 0 1996 John Wiley & Sons, Inc. I NTRODUCTIO NLatexes containing epoxy groups have been prepared and investigated for many years. These latexes find their application especially in waterborne coatings,'-but their use has been investigated for a wide variety of other applications as In coatings, epoxy groups can act as crosslinking sites by which mechanical properties can beThe monomer commonly used to incorporate an epoxy group is glycidyl methacrylate (GMA). The epoxy group is sufficiently stable to hydrolysis to allow its incorporation in latex particles by means of emulsion polymerization. However, although it is known that a major part of the epoxy groups remains intact during an emulsion polymerization, the minor part that has hydrolyzed may give rise to side reactions.ls2 Furthermore, the hydrolysis product of GMA itself, 172-dihydroxypropyl (or glyceryl) methacrylate, is a water-soluble monomer that might have an influence on the emulsion polymer-~ ~~ * To whom correspondence should be addressed.Journal of Applied Polymer Science, Val. 61, 9-19 (1996) ization process. One of the possible consequences is that hardly any significant extent of epoxy functionality is located at, or close to, the surface of the particles.Another problem when using GMA may be the occurrence of crosslinking inside the latex partic l e~.~~~ This intraparticle crosslinking prevents proper control of the molecular mass and may have an adverse effect on the final properties of the latex.Our incentive to investigate the preparation of epoxy-functional latexes is that the latter will be studied in their crosslinking behaviour toward amino-functional latexes." For this purpose, it is important to control the amount and position of the epoxy groups in the latex and to control the molecular mass of the copolymer. To this end, the influence of several parameters was investigated, especially the influences of chain transfer agents and of reaction temperature on the molecular mass and the degree of i...

Toward Functionalized Polyolefins from the Hydrogenation of Isoprene–Glycidyl Methacrylate Copolymers Prepared by Reversible Deactivation Radical Polymerization in Heterogeneous Media

“…Therefore, in further reactions, it was decided to reduce the GMA concentration, since this behavior was attributed to possible interactions of the epoxy group with the surfactant that led to colloidal instability. The copolymerization procedure that was finally used was similar to the homopolymerization method with some differences and characteristics that follow: to avoid or reduce the cross-linking reactions associated with the GMA as well as the colloidal instability, sodium bicarbonate was added to the SDBS aqueous solution to increase the pH of the reaction mixture; , the reaction temperature was decreased to 105 °C; in the NMP reactions ( RXN 2 and RXN 3 ), TEMPO was replaced by N - tert -butyl- N -(2-methyl-1-phenylpropyl)- O -(1-phenylethyl) hydroxylamine (universal alkoxyamine, UA); and in the RAFT reactions ( RXN 4 and RXN 5 ), 0.4303 g (1.066 mmol) of 4-cyano-4-(do­decyl­sulfanyl­thiocarbonyl)­sulfanylpentanoic acid as RAFT agent were employed and the KPS initiator was replaced by 0.0164 g (0.068 mmol) of benzoyl peroxide and 0.0432 g (0.222 mmol) of tert -butyl perbenzoate ( RXN 4 ) (to ensure the continuous presence of radicals during the reaction and maintain the living-dormant equilibrium). During the stage of continuous monomer addition (semicontinuous regime), a smaller flow was used in some reactions, compared to the homopolymer case, to end up with a lower solids content in the latex (15%–19%). Isoprene monomer was added first and, immediately after its addition ended, the GMA addition started.…”

“…Isoprene monomer was added first and, immediately after its addition ended, the GMA addition started. Regarding the addition of sodium bicarbonate as pH buffer, German et al reported the addition of NaHCO 3 to GMA copolymerization reactions to get better stability in the emulsions, avoiding the formation of methacrylic acid from the methacrylic monomers, which may lead to an unfavorable shift in the acid–base equilibrium of the emulsifier, destabilizing the emulsion. In addition, at relatively high concentrations of GMA in acid media, the epoxy group may undergo acidic hydrolysis and further reaction with other epoxy groups leading to polymer cross-linking, so the pH of the media must be carefully adjusted to avoid colloidal instability and/or cross-linking.…”

“…to avoid or reduce the cross-linking reactions associated with the GMA as well as the colloidal instability, sodium bicarbonate was added to the SDBS aqueous solution to increase the pH of the reaction mixture; , …”