Influence of the linkage type between the polymer backbone and side groups on the surface segregation of methyl groups during film formation. Issue 47 (29th September 2015)

• Record Type: Journal Article
• Authors: Zhang, Yizhi; Fan, Hao; Wang, Yuping; Zuo, Biao; Zhang, Wei; Wang, Shunli; Wang, Xinping
• Is Part Of: Soft matter. Volume 11:Issue 47(2015)
• Page Start: 9168
• Page End: 9178
• Publication Date: 2015-09-29
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c5sm01504a
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : A large difference in the concentration-dependent surface structures of the cast PMA and PVAc films was caused by the reversed position of the ester group. Abstract : Although poly(vinyl acetate) (PVAc) differs from poly(methyl acrylate) (PMA) only in the reversed position of the ester group, a large difference in the concentration dependence of the casting solution on the corresponding surface structure of the cast films of PVAc, PMA and poly(methyl methacrylate) (PMMA) was observed. The hydrophobicity of both PMA and PMMA films increased with increasing concentration of the corresponding polymer solution, whereas cast PVAc films showed the reverse trend. The surface structure of the cast films prepared with different concentrations of the casting solution, characterized by sum frequency generation (SFG) vibrational spectra, showed that the order of the methylene groups increased while that of the acetyl methyl group decreased on the surface of cast PVAc film with increasing concentration of casting solution. However, the order of the ester methyl group increased and that of methylene groups did not change for cast PMA films with increasing concentration of casting solution. The cast PMMA film showed a reverse trend compared with the corresponding PMA film. It is apparent that well-ordered ester or acetyl methyl groups on the surface, which are oriented away from the polymer film, rather than methylene groups, play an important role in determining surface hydrophobicity, as the latter shield the OCO groups of PVAc, PMA and PMMA film surfaces from being exposed, resulting in low surface free energy. The reason for this difference is attributed to the relatively low energy for ester methyl group reorientation, an ester group structure nearer to the trans state and more regular local configuration of segments in concentrated solutions of PMA and PMMA compared to that of PVAc.