Preparation and reversible photo-crosslinking/photo-cleavage behavior of 4-methylcoumarin functionalized hyperbranched polyester

• Published in: Polymer (Guilford) Vol. 49; no. 23; pp. 4981 - 4988
• Main Authors: Fu, Qi, Cheng, Liangliang, Zhang, Yong, Shi, Wenfang
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 30.10.2008; Elsevier
• Subjects: 4-Methylcoumarin; Applied sciences; Chemical modifications; Chemical reactions and properties; Exact sciences and technology; Hyperbranched polyester; Organic polymers; Physicochemistry of polymers; Thiol–ene addition; Hyperbranched polyester; 4-Methylcoumarin; Thiol–ene addition; Photosensitivity; Photochemical crosslinking; End group; Branched polymer; Coumarine derivatives; Ester polymer; Reversible reaction; Mercaptoacid; Thiol-ene addition; Esterification; Chemical modification; Light sensitive polymer; Aliphatic polymer; Preparation; Addition reaction; Hydroxyl group; Sulfur containing polymer; Chemical reactivity
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2008.09.017

A novel hyperbranched polymer endcapped with 4-methylcoumarin group (MCTH40) was prepared via thiol–ene addition reaction of thiol-modified hyperbranched polyester (fully thioglycolic acetate of Boltorn™ H40, TAH40) with a vinyl monomer (7-(4-vinyl-benzyloxyl)-4-methylcoumarin, VBMC), and characterized with 1H NMR and FT-IR spectroscopies. Its reversible photo-crosslinking/photo-cleavage behavior was evaluated based on the UV–vis spectroscopic analysis, and compared with the linear polymer, poly(7-(4-vinyl-benzyloxyl)-4-methylcoumarin (PVBMC)). The absorbance at 319nm in the UV–vis spectrum gradually decreased under UVA irradiation (λmax=365nm), and then rapidly recovered under UVC irradiation (λmax=254nm). The fluorescence intensity of MCTH40 (λmax=469nm) recovered to 85.2% of original level after photo-cleavage under UVC irradiation, higher than 83.5% of PVBMC (λmax=472nm). The UV–vis analysis results indicated that MCTH40 performs more rapid photo-response than linear PVBMC under the same conditions. Furthermore, the average doses of UVA irradiation for the maximum degree of photo-crosslinking were 22.08Jcm−2 for MCTH40 and 28.29Jcm−2 for PVBMC. The average UVC doses of complete photo-cleavage were 9.44Jcm−2 for MCTH40 and 9.58Jcm−2 for PVBMC. The GPC analysis indicated that the average molecular weight and its PDI of MCTH40 showed a slight increase after three reversible cycles. [Display omitted]