| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 가을 (10/13 ~ 10/14, 제주 ICC) |
| 권호 | 30권 2호 |
| 발표분야 | 고분자 합성 |
| 제목 | Ambidextrous Surfactants for Water-Dispersible Polymer Powders from Dispersion polymerization of MMA in supercritical CO2 |
| 초록 | Semifluorinated copolymers have attracted much attention due to their unique properties such as low surface energy, chemical/biological inertness, and oil/water repellence. They may be utilized in various applications for example, surfactants in liquid and supercritical carbon dioxide, biomaterials, membranes, coatings, etc. Random copolymers are of interest because they have many industrial applications and can be synthesized more easily and affordably than block copolymers Recently, polymerization in supercritical carbon dioxide has received significant attention as an alternative to the conventional polymerization process. In the conventional processes, Poly(methyl methacrylate) (PMMA) has been prepared by bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, or dispersion polymerization. Except for the bulk polymerization, all other methods are using water, solvents or organic diluents. Therefore, these polymerization methods are harmful to human beings and to our environment. Carbon dioxide is rapidly becoming an attractive alternative to liquid solvent since it is an environmentally benign which has the potential to eliminate the production of organic and aqueous waste streams in manufacturing facilities. For this reason, scCO2 has been studied extensively as a polymerization medium as it is cheap and nontoxic. Because scCO2 is a poor solvent for polymerization, an effective stabilizer is necessary to disperse the growing polymer chains in the reaction medium. A number of stabilizer architectures based on block and graft copolymer fluorinated materials have been described. The resulting polymer suspension in supercritical fluid was expanded rapidly to make surface coatings and stable aqueous latexes. In this work, PDMAEMA-ran-PFOMA copolymers were employed as a dispersant for the polymerization of MMA in scCO2, and the effects of FOMA ratio and DMAEMA groups of stabilizers were investigated. The copolymers were synthesized by free radical polymerization of DMAEMA and FOMA in presence of AIBN at 65oC. Because of the presence of PDMAEMA units, the resultant copolymers are unlike PFOMA in that they dissolved in chloroform and other organic solvents. The results from the synthesis of PDMAEMA-ran-PFOMA and their characterization are summarized in Table 1. The proportion of each monomer in the copolymers was thus calculated from 1H NMR spectra of copolymers. As expected, the proportion of DMAEMA and FOMA incorporated in the copolymers is similar to the feed ratios of monomers. The solubility of the copolymers in dense scCO2 was studied in the temperature range 35~60oC and pressure up to 345 bar. The results in Figure XX indicated that most copolymers are soluble in scCO2 at these conditions. The optically transparent one-phase region is above each curve in the plot. It is well-known that the PFOMA component is very CO2-philic so the solubility of random copolymers in CO2 increases with the mole fraction of PFOMA. The copolymer containing 75mol % PDMAEMA was soluble in CO2 at 65oC and 400 bar. With the semifluorinated random copolymers as the stabilizer, the polymerization reactions of MMA started out homogeneously and then formed a colloidal dispersion of PMMA that flocculated later during the polymerization. Upon venting the CO2, a dry white free-flowing powder remained in the reaction vessel. The PMMA obtained from these successful dispersion polymerizations was in the form of spherical particles in higher yields and higher molecular weight PMMA with narrow particle size distributions. From the SEM analysis of the prepared PMMA, it is found that spherical PMMA was prepared with both types stabilizers and the size of PMMA decreased with increasing FOMA ratio of stabilizer. |
| 저자 | 황하수1, H. Yuvaraj2, 이민영2, 김원수2, 임권택2 |
| 소속 | 1부경대, 2이미지시스템공학과 |
| 키워드 | dispersion polymerization; carbondixide; semifluorinated; MMA; Styrene |
