Butyl Acrylate RAFT Polymerization In Miniemulsion And Synthesis Of Poly(Styrene-b-Butyl Acrylate-b-Styrene) Block Copolymer

Living/controlled free radical polymerization (CLRP), providing a facile route to the synthesis of polymers with precise microstructures, can be used to tailor-make polymer materials. In the past decade, CLRP has attracted much attention, being one of the most popular topics in the polymer chemistry. Among the three major CLRP approaches, reversible addition-fragmentation transfer (RAFT) polymerization has clear advantages in terms of a larger variety of monomers and much higher polymerization rate when applied in (mini)emulsion. On the other hand, (mini)emulsion polymerization, where the polymerization is carried out in water, is friendly to the environment, ease to remove the polymerization heat, and easy to handle. It is desirable to carry out CLRP in (mini)emulsion from point of view of commercial implementation. RAFT (mini)emulsion polymerization shows very promising in the commercial applications.Among the most-used industrial monomers, RAFT miniemulsion polymerization of styrene, methyl methacrylate, vinyl acetate and their derivative have been successfully achieved. The only exception is butyl acrylate (BA). The major obstacle is the colloidal instability during the polymerization.In this thesis, it is found from a theoretical simulation that the RAFT miniemulsion polymerization of BA is more apt to undergo the superswelling in the beginning of the polymerization than styrene does, which leads to the colloidal instability. Inspired by the results of the simulation, we proposed that the stability of BA RAFT miniemulsion could be improved by reducing the chain transfer rate constant of RAFT agent. In order to testify the hypothesis, four different RAFT agents, benzyl dithioisobutyrate (BDIB), 1-phenylethyl phenyldithioacetate (PEPDTA), cumyl dithioisobutyrate (CDIB) and benzyl dithiobenzoate (BDTB), were designed and evaluated in BA bulk and miniemulsion polymerization. Even though all RAFT agents mediate the bulk polymerization in a well-controlled manner, only BDIBresults in good control over the miniemulison polymerization, as indicated by M_n linear growth with monomer conversion and rather low PDI. GPC curves of PBA controlled by PEPDTA have a shoulder peak at the high monomer conversion, and the GPC curves of PBA controlled by CDIB and BDTB all show the dual peaks. The results of the experiments are well consistent with the theoretical predictions. It is concluded that the good control over BA miniemulsion polymerization can be achieved only with the RAFT agent of low chain transfer rate constant, for example, using isopropyl as Z group and benzyl as the R group.A tri-block copolymer was synthesized with BA as soft middle block and St as the first and third block. The experiments show that the feeding monomer must transfer into the particles as soon as possible, and feeding the monomer in emulsion can lead to a lower PDI. The particle size distribution must be narrow after completing the first block to make sure the block copolymer has uniform composition and narrow PDI. The very high monomer conversion to end the first block should be avoided to synthesize the tri-block copolymer with low PDI. As suggested from the physical properties, the synthesized tri-block copolymer can be used as a modifier of bitumen and polymers, ingredient in formulating compounds for footwear applications, formulating adhesives, sealants, and coatings.