Preparation Of Butyl Acrylate/acrylamide Copolymer And Its Composite With Nano Particles Through Ultrasonic Emulsifier-free Emulsion Polymerization

A new technology, combining two kinds of environmental protection and economical methods, which are emulsifier-firee emulsion polymerization and ultrasonic irradiation, is proposed in this paper. That is ultrasonic emulsifier-free emulsion polymerization. Under no chemical initiators and emulsifiers, BA/AM copolymer and BA/AM/ST, BA/AM/VA and BA/AM/MMA etc. ternary copolymer are prepared through this method. This method is successfully introduced into the preparation of the composite of polymer/inorganic nano-particles, and a series of composite of BA/AM/nano-SiO2, BA/AM/nano-TiO, BA/AM/nano-Fe3O4 etc. are prepared by this method. This method offers a new method and technology for preparing polymer particles, polymer/inorganic nano-particles composite, and solves the questions of dispersion, stabilization and composite of nano particles in polymer.Using the dispersion, agitation, emulsification and initiation of ultrasound, the ultrasonic emulsifier-free emulsion polymerization of BA/AM was realized. And BA/AM copolymer was prepared by this method. All kinds of affection factors were studied. The results showed there were only two regions, which are acceleration and deceleration region, and no constant velocity region. And the polymerization process was similar to microemulsion polymerization. If acoustic intensity were increased, the monomer conversion and polymerization rate wouldincrease. The affection of reaction temperature to monomer conversion was complicated, however, higher or lower temperature would decrease the monomer conversion. Moreover, inorganic salt made a very important role in polymerization. If there were no inorganic salt in reaction system, no emulsion was produced. Too much inorganic salt would destroy the electric double layer of particles and decrease the stabilization of emulsion and polymerization rate. Furthermore, the influences of acoustic intensity and reaction time to particles diameter and distribution were studied. While the reaction time was about 40-50min, the particle diameter suddenly decreased, then it maintained a constant value. The influences of acoustic intensity to particles diameter was complicated, higher and lower acoustic intensity would increase the particles diameter. DSC results indicated that the sample after purified only had one gamma transition. The FTIR spectra showed that the sample after purified was the copolymer of BA and AM, but not the blend of poly(butyl acrylate) and polyacrylamide. Moreover, TEM photographs showed that the particles had clearly double layer configuration, the outer layer was the copolymer of BA and AM and the inner layer was PBA.The polymerization mechanism of ultrasonic emulsifier-free emulsion polymerization was also studied. The results showed that primary free radicals came from the breakage of AM molecules, and abundant PAM macromolecules chains were formed in aqueous phase. Moreover, the character of lipophilicy monomers would influence polymerization process. According to the main reaction loci and the monomer conversion, the polymerization course was divided into four stages. (1) At the beginning, AM molecules polymerized preferentially in the aqueous phase. As the chain length of polyacrylamide increased, its hydrophilicity rapidly depressed. (2) So the BA molecules could react with polyacrylamide chain and form the micelle-like structure. (3) After the particles formation by the aggregation of the micelle-like structure, BA polymerized exclusively in the particles, but the AM continuously mainly polymerized in the aqueous phase because of the cavitation bubble produce by ultrasound. (4) After the disappearance of BA droplets, the sources of BA supply to the particles, the main reaction locuswas transferred from the particles to the aqueous phase.On the base of ultrasonic emulsifier-free emulsion polymerization of B A/AM, the ternary copolymer of BA/AM/ST, BA/AM/MMA and BA/AM/VA were prepared by through introducing the third component. The results showed that monomer conversion increased with the reaction time. While acoustic intensity achieved a value, however, the monomer conversion decreased. Higher and lower reaction temperature both decreased the monomer conversion. Furthermore, the laser particle diameter analyzer showed that the particles diameter was not sensitive to reaction time and it was about 80nm. However, the particles diameter was double peak distribution at initial stage, but it became single peak distribution at later stage. FTIR spectrum showed that the sample after purified contained characteristic peaks of all kinds of monomers and proved the sample was copolymer, but not the blend of homopolymers. DSC spectrum indicated the content of ST in the BA/ST/AM ternary copolymer by ultrasonic method was higher than that of ST by conventional emulsifier-free emulsion polymerization method. TEM photographs showed that the particles diameter was obviously lower than that by through conventional method.The composite of BA/AM/nano-SiCh, BA/AM/nano-TiO2 and BA/AM/nano-Fe3O4 were prepared by through ultrasonic emulsifier-free emulsion polymerization. However, the inorganic nano particles must be pre-treated with BA. FTIR spectra showed that the nano particles after treated with BA had the characteristic peaks of BA. The results showed the monomer conversion and polymerization rate would increase with increasing acoustic intensity. Polymerization course could be divided into two stages, that is acceleration and deceleration stage. Moreover, the monomer conversion would increase with the increase of content of AM in recipe under the same reaction time and acoustic intensity. However, more increasing the content of AM would decrease the monomer conversion. FTIR and DSC spectra indicated the polymer on surface of nano particles was the copolymer of BA and AM, and the inorganic nano particles were nicely dispersed in these polymers. The sample obtained by this way was notthe blends of three materials. TEM photographs showed that the nano-TiO2 was not encapsulated with polymer but equably dispersed in polymer. This indicated that besides reaction condition and pre-treated nano particles, the intrinsic properties of inorganic nano particles would influence the process of polymer encapsulating nano particles. The particles diameter analysis showed the average particle diameter was about 400-500nm.