Investigation of the copolymerization of butyl acrylate (BA) with vinyl neononanoate (VeoVA-9)

[摘要] ENGLISH ABSTRACT: This study has the goal of illuminating structure-properties relationships for copolymers ofvinyl neononanoate (VeoVa-9) and butyl acrylate (BA). The VeoVa-9/BA copolymers wereprepared using solution free radical copolymerization and miniemulsion copolymerization.The free radical copolymerization of VeoVa-9/BA at different feed ratios in benzene at 80°Cusing 2,2'azobis (2-methylpropionitrile) (AIBN) as initiator was investigated. The tenninalmodel was used to describe the copolymerization of these monomers and the copolymercomposition was detem1ined using I H NMR spectroscopy. The reactivity ratios, estimatedusing the nonlinear least square method, and the 95% confidence interval giving values of thereactivity ratios, which were 0.042 (±0.014) and 6.95 (-0.53 /+0.65) for the VeoVa-9 and BArespectively. The copolymerization kinetics for the VeoVa-9/BA was investigated byfollowing individual monomer consumption rates by in-situ NMR. The use of this methodprovides useful information about the individual monomer concentration during the course ofreaction. The copolymerization reaction shows a higher tendency for BA to react than theVeoVa-9.The copolymerization of these monomers was also investigated in a heterogeneous systemusing the miniemulsion technique. In these investigations the effect of surfactant, initiatortype and water solubility of the monomer on the batch and semi-batch miniemulsionbehaviour was demonstrated. The rate of the miniemulsion polymerization increased withincreasing surfactant concentration, while the final particle size of the latex decreased withincreasing surfactant concentration in the miniemulsion mixture. Two types of initiators wereused, water and oil-soluble initiators (ammonium persulphate (APS) and AIBN respectively).The rate of the batch miniemulsion polymerization showed dependency on the type ofinitiator used as the monomer conversion increased faster with APS than when using AIBN.The average final particle size was also larger when the AIBN was used than it was when theAPS was used. The batch miniemulsion showed an increase in the nucleation (inhibition)period and a slower polymerization rate as the VeoVa-9 concentration increased. The increasein the VeoVa-9 concentration in both batch and semi-batch miniemulsions also led to anincrease in the particle size.The obtained copolymers were characterized in terms of their chemical composition viatwo-dimensional chromatography (2-D), and in tern1s of some of their physical propertiesusing dynamic mechanical analysis (DMA) and contact angle measurement. The 2-D analysisshowed that all the BA was incorporated in the copolymer; this result was also confinned byIH NMR. The 2-D analysis also showed that the copolymer composition depends on themonomer addition mode in the semi-batch process. The copolymer glass transitiontemperature (Tg) value showed an increase as the VeoVa-9 concentration increased and the Tgvalues of the copolymers ranged between the two homopolymers' Tg values. Thehydrophobicity of the copolymers increased as the VeoVa-9 concentration increased as wasindicated by contact angle measurements.

[发布机构] Stellenbosch University