Grafting photochemical initiated

We repeated this grafting reaction [100] by photochemical initiation and we showed that if the addition onto the 1,2 double bands was favored, the fluorinated thiols could be grafted onto all double bands of PBHT and diols with a fluorine amount of 55% could be obtained. Moreover, this study shows an improvement of the dispersion (observed in G.P.C.) when the grafting was realized by photochemical initiation in comparison to that realized by classical initiators. 

N-Benzyl and iV-alkoxy pyridinium salts are suitable thermal and photochemical initiators for cationic polymerization, respectively. Attractive features of these salts are the concept of latency, easy synthetic procedures, their chemical stability and ease of handling owing to their low hygroscopicity. Besides their use as initiators, the applications of these salts in polymer synthesis are of interest. As shown in this article, a wide range of block and graft copolymer built from monomers with different chemical natures are accessible through their latency. 

Such functionality can also be of great practical importance since functional initiators, transfer agents, etc. are applied to prepare end-functional polymers (see Section 7.5) or block or graft copolymers (Section 7.6). In these cases the need to maximize the fraction of chains that contain the reactive or other desired functionality is obvious. However, there are also well-documented cases where weak links formed by initiation, termination, or abnormal propagation processes impair the thermal or photochemical stability of polymers. 

Usually, free-radical initiators such as azo compounds or peroxides are used to initiate the polymerization of acrylic monomers. Photochemical and radiation-initiated polymerizations are also well known. Methods of radical polymerization include bulk, solution, emulsion, suspension, graft copolymerization, radiation-induced, and ionic with emulsion being the most important. 

UV light induced grafting onto wood cellulose is reported for several vinyl monomers. The reaction is initiated by free radical initiators such as phenylace-tophenone and benzophenone derivatives. Percent grafting-time conversion curves are determined as a function of the initiators, monomers, pulps and additives. Additional typical results obtained in IR spectroscopy, GPC and thermal analysis are reported. A discussion about the use of a photochemical procedure in obtaining cellulose graft copolymers is presented. 

The present report extends our work to the photografting of various monomers, using several photo-initiators, onto wood cellu-losic materials. Moreover, it gives the possibility to discuss some problems related to the photochemical grafting. 

Copolymers of 2,3-butanedione-2-< -methacryloyl-oxime with MMA [poly (BOMA-co-MMA)], containing different amounts (7-30 mol%) of side-chain O-acyloxime moieties, have also been used [75] as macro-initiators for the photochemical grafting of styrene and acrylamide in benzene and dioxane solution, respectively,... 

Synthetic strategies associated with grafting employ various modes of polymerizations, for example, living/controlled techniques, thermally initiated or photoini-tiated polymerizations. Among these, photochemical technique offers a number of advantages. First of all, it can be conducted at room temperature. This is quite remarkable when low manufacturing costs are concerned for mass production, as well... 

Based on the membrane surface properties and the HA properties, various researchers have attempted to change the membrane surface characteristics by surface modification. Different techniques have been performed, such as ion beam irradiation, plasma treatment, redox-initiated graft polymerization, photochemical grafting, and interfacial polymerization (IP). In this chapter, two surface modification techniques, IP and photochemical grafting, are discussed by means of experimental examples. The surface characteristics of the unmodified membrane and the modified membranes are studied and their relationships with irreversible fouling and NF performance are reported. 

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