| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 봄 (04/14 ~ 04/15, 전경련회관) |
| 권호 | 30권 1호, p.527 |
| 발표분야 | 고분자 합성 |
| 제목 | Dispersion polymerization of MMA in supercritical CO2 in the presence of semifluorinated random copolymers |
| 초록 | Summary Random copolymers of poly(oligo(ethylene glycol) methacrylate) (POEGMA) -ran-poly(1H,1H,2H,2H-perfluorooctylmethacrylate) (PFOMA) and poly(2-dimethylamino ethylmethyacrylate) (PDMAEMA)-ran-PFOMA have been synthesized in supercritical carbon dioxide via free-radical copolymerization. A comparative study of surfactant activities on the polymerization of MMA in supercritical carbon dioxide was carried out with these semifluorinated random copolymers. PMMA particles stabilized with a PDMAEMA-ran-PFOMA could also form stable latex in aqueous solution of HCl. Introduction 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.[1-4] Random copolymers are of interest because they have many industrial applications and can be synthesized more easily and affordably than block copolymers. Carbon dioxide is rapidly becoming an attractive alternative to liquid solvent since it is an environmentally benign medium 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.[1] In this work, PDMAEMA-ran-PFOMA, POEGMA-ran-PFOMA copolymers were employed as a dispersant for the polymerization of MMA in scCO2, and the effects of FOMA ratio and OEGMA and DMAEMA groups of stabilizers were investigated. Experimental In a typical polymerization for statistical copolymer of OEGMA and FOMA, 0.2 g of OEGMA, 0.8 g of FOMA and 0.01 g AIBN and teflon-coated stir bar were introduced into a stainless steel reactor (4ml). The reactor was pressurized by ISCO syringe pump (Model 260D) containing compressed CO2. The polymerization was conducted in supercritical CO2 at 65oC, 345 bar for 8 hrs. After polymerization, any unreacted monomers were extracted with liquid CO2. For the dispersion polymerization of MMA in scCO2, 0.5 g of MMA, 0.015g of PDMAEMA-ran-PFOMA (37:63), 0.005g (1wt% of monomer) of AIBN, and a teflon-coated stir bar were introduced into a stainless steel reactor (4ml). The reactor was pressurized by ISCO syringe pump (Model 260D) containing compressed CO2. The polymerization was conducted at 65oC, 345 bar for 10 hrs. After polymerization, any unreacted MMA was extracted with liquid CO2 and the product was collected and weighed. Results & Discussion Statistical copolymerizations were carried out in supercritical CO2 in the presence of AIBN. After 8 hr of polymerization at 65 oC, the conversions were determined in the range 75 – 80 %. The solution was clear for 39:61 molar OEGMA-FOMA copolymer and 37:63 molar DMAEMA-FOMA copolymer during the reaction. On the other hand, the solution became slightly cloudy at the end of polymerization for higher OEGMA copolymer of 65:35 molar composition due to a formation of micellar aggregates. For most of copolymerizations of POEGMA-ran-PFOMA, the conversion of OEGMA was higher than FOMA. 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. 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. PDMAMEA-ran-PFOMA (37:63) resulted in smaller and more uniform particle size ( ~ 1 mm) compared with POEGMA-ran-PFOMA (39:61). This may be explained that DMAEMA chain provides better stability to the growing PMMA particles. In addition, latex particles synthesized in CO2, which were stabilized by PDMAEMA-ran-PFOMA could be redispersed in an aqueous solution of 0.1N HCl. Thus, PDMAEMA-ran-PFOMA copolymers are regarded as ambidextrous surfactants because they stabilize latexes both in CO2 and water media.[5] |
| 저자 | 황하수, 임권택 |
| 소속 | 부경대 |
| 키워드 | carbon dioxide; dispersion polymerization; semifluorinated copolymer |
