AGGREGATION BEHAVIOR OF POLY(METHACRYLIC ACID) WITH CUCURBIT7URIL IN AQUEOUS SOLUTION
Cucurbitnurils (n=5-10) have been gradually established as versatile host molecules for the host-guest interactions 13, since the elucidation of the molecular structure of cucurbit6uril by Mock in 1981 4. Taking advantage of cucurbitnurils, various mechanically interlocked molecules including rotaxanes and (pseudo)polyrotaxanes have been synthesized by Kim 5, Buschmann6 and others 7. Cucurbit7uril (CB7) in several cucurbituril homologues has been extensively used for the host-guest chemistry due to its better water-solubility than others. CB7, a water soluble barrel-shaped host, consists of 7 glycoluril groups and 14 methylene bridges at both ends. The two rims are formed by the glycoluril carbonyl oxygens, thereby are negatively charged, and they develop ion-dipole interactions with cationic guests 8-9. Poly(methacrylic acid), PMAA, represents an fascinating case for investigation, since the hydrophobic interactions, which were introduced by the methyl groups of PMAA, result in hypercoiling of the polymer in acid media 10-121. And such conformation could increase the solubility of organic compounds such as arenes and alkanes in the aqueous solution of the polymer. It should be noted that Ph is important for the conformation of PMAA in aqueous solution. Upon adding the base to the solution of PMAA, the carboxylic acid groups ionized and negative charges were obtained. The non-uniform, sudden transformation of the conformation, which is irreversible, from the hypercoiled to extension is due to the increase of Coulombic repulsive forces. It is expected that this conformational alteration may be used as the basis of the design and synthesis of new smart hybrid materials, such as films and hydrogels. In this study, we investigated the aggregation behaviors of PMAA with CB7 in absent and present of NH_4OH in aqueous solution by dynamic light scattering, fluorescence techniques, and resonance light scattering. Figure 1 shows that the average hydrodynamic radius of PMAA increases with adding CB7. It is considered that the aggregates were formed between CB7 and H+of PMAA by the hydrogen bonding interaction. With increasing the concentration of CB7, the increase of the hydrogen bonding interaction between CB7 and H+of PMAA causes the transition between the intrachain and interchain association by the interaction of the two COO and one+HCB7H+. With the addition of NH_4OH, CB7 could combine with both the free NH_4T by the electrostatic and iondipole interactions and the free I-T of PMAA by the hydrogen bonding interaction, and the size of the aggregates also increases with increasing the concentration of CB7 because that the free NH_4+in the solution as bridges enhance the host-guest interactions between PMAA and CB7. Figure 2 show the RLS spectra of the aggregation of ammonium poly(methacrylate) with different concentrations of CB7.
Hui Yang Jingcheng Hao Yebang Tan
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R.China The Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Jinan250100, PR China
国际会议
PP’2010，Jinan International Symposium on Polymer Physics(2010济南国际高分子物理学术研讨会)
济南
英文
336-337
2010-06-06（万方平台首次上网日期，不代表论文的发表时间）