Photochemical cross linking

Tanaka and E. Otomegawa, J. Polymer Sci., Polymer Chem., 1974,12, 1125 T. Nishikubo, T. Ichijo, and T. Takaoka, J. Appl. Polymer Sci., 1974,18, 2009 T. Nishikubo and T. Ichijo, Nippon Kagaku Kaishi, 1974, 45. 

A new cross-linking chroraophore has been investigated, based upon the 4-(or 4 -)substituted benzylideneacetophenone (chalcone) molecule.61 The photocross-linking of epoxyacrylates has recently been studied quantitatively.62 A novel kind of polymer containing the diazofluorene moiety (8), synthesized from 

The photochemical cross-linking of polyethylene has been described.66 

The patents literature relating to photopolymerization is reviewed in the Appendix. 

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Sulfurized olefins (S2CI2 plus isobutene) are further reacted with S and Na2S to give products useful as extreme pressure lubricant additives (144,145). The reaction of unsaturated natural oils with sulfur monochloride gives resinous products known as Factice, which are useful as art-gum erasers and mbber additives (146,147). The addition reaction of sulfur monochloride with unsaturated polymers, eg, natural mbber, produces cross-links and thus serves as a means for vulcanizing mbber at moderate temperatures. The photochemical cross-linking of polyethylene has also been reported (148). 

Of great importance for both the formation and photochemical cross-linked of organotin oligomers and polymers is the tin atom in the coordination-bound state. 

The observed spectral changes suggest the following photochemical cross-linking mechanism for oligoorganoepoxystannanes ... 

Then, it appears, that photochemical cross-linking of an organotin copolymer is the result of complex supramolecular conversions and intermoleeular reactions of anhydride and organotin units involving the formation of transverse coordination-bound organotin carboxylate fragments 109). 

It follows from these findings that the simultaneous presence of both anhydride and organotin groups in the copolymer structure and their regular distribution among the macromolecular chain is a prerequisite for photochemical cross-linking of a polymer. 

These results emphasise the important role played by HC1 not only as a catalyst for the dehydrochlorination process but in influencing the distribution of polyene sequences which result from the primary part of the degradation process and the photochemical cross-linking reactions of the polyenylic cations. 

Kiehm, D., and Ji, T.H. (1977) Photochemical cross-linking of cell membranes. J. Biol. Chem. 252, 8524-8531. 

In arrays of closely packed nucleosomes composed of all four core histones, strands of H2A-H2B dimers could be incorporated in the grooves between the two H3-H4 strands, producing a four-stranded polymer. Alternatively, they could bind to the H3-H4 double-stranded fiber to give an octamer of the histones per nucleosome. This latter model is supported by the photochemical cross-linking of histones to DNA which have shown that within the nucleosome core the four core histones are not equivalently positioned with respect to... 

Post-Treatment of Hollow Fibers. End use of ihe hollow-fiber membrane dictates the ty pe of post-tre.iiment. if any There are three main categories fibers thal are spun, fibers that vv ill be chemically or physically modified, and fibers that will serve as a porous matrix lor support ol another lactivc) polymer deposited (nr entrapped) upon (or within) its walls. There is no theoretical impediment to the inclusion of all conventional treatments in the spinning line photochemical cross-linking, llmirinniion, and anliplaslici/ers have been successful. 

Fig. 12 Illustration outlining MIP film fabrication. The C-terminus nonapeptide epitope is attached through a tether to a glass or oxidized silicon surface by the N-terminal amino acid of the peptide. Monomers are photochemically cross-linked while remaining in contact with the peptide modified surface. Following polymerization, the glass substrate is removed. The protein can now bind to the MIP via its C-terminus nonapeptide epitope. Modified from [114]...

Chong, P. C., and Hodges, R. S. (1982). Photochemical cross-linking between rabbit skeletal troponin and alpha-tropomyosin. Attachment of the photoaffinity probe N-(4-azidobenzoyl-[2-3H]glycyl)-S-(2-thiopyridyl)-cysteine to cysteine 190 of alpha-tropomyosin. / Biol. Chem. 257, 9152-9160. 

In the V-ATPase, the presence of at least two peripheral stators has been reported (Boekema et al., 1999 Domgall et al., 2002 Wilkens et al., 1999, 2004). Candidates for the stator proteins in the V-ATPase are subunits E and G, and support for this assignment comes from photochemical cross-linking studies that place these subunits on the outside of the Vi domain for much of its length (Arata et al., 2002a,b). Another subunit that probably plays the role of a stator in the V-ATPase is the a-subunit of the Vo- The Vo a-subunit has a large cytoplasmic domain, and it has been shown that this domain interacts with the A-subunit of the Vi (Landolt-Marticorena et al, 2000). 

Cinnamates occupy an important place in the history of photochemistry. Schmidt and his co-workers [18] used the solid state photochemistry of cinnamic acid and its derivatives to develop the idea of topochemical control of photochemistry in the crystalline state. Minsk [19] developed poly(vinyl cinnamate) as the first polymer for photoimaging. The cinnamate chromophore is still commonly incorporated in photopolymers of all types, including LC polymers, to enable them to be photochemically cross-linked [20], and a number of reports of the photochemistry of such MCLC and SCLC polymers are summarized below. 

Tazuke, Ikeda, and their co-workers [53,54] were the first to use phenylene-diacrylate (PDA) as a mesogen and chromophore to explore the possibility of forming two-dimensionally reinforced polymer materials by photochemical cross-linking of a thermotropic LC polymer. Polyesters, 23, of para-phenylene-diacrylic acid and several diols were synthesized and found to exhibit LC behavior upon annealing above Tg. Polymer 23a exhibited [53] the texture of a N meso-... 

Dictamine) Afraegle paniculata, Dictamnus albus, (photochemical cross-linking)... 

Bitan G, Teplow DB. Rapid photochemical cross-linking-a new tool for studies of metastable, amyloidogenic protein assemblies. Acc. Chem. Res. 2004 37 357-364. 

Oligonucleotide duplexes containing the benzophenone-modified nucleoside (75) have been shown to undergo a reversible photochemical cross-linking reaction. ° The benzophenone is located in the major groove. On photolysis, a new product is formed, which the authors were unable to characterise, but, based on model reactions, the benzophenone modified thymidine derivative (76) is postulated. On heating at 90°C the cross-link is reversed. 

Photopolymerization, that is, a polymerization process initiated by photochemical production of the reactive species initiators (Section 6.8.1), is largely used in industry. Polymers can be synthesized by photoinitiation, but can also be modified by photochemical cross-linking (photochemical hardening or UV curing photoimaging photolithography see Special Topic 6.27). 

Polymerization of reactive monomeric liquid crystals is one method for stabilizing the liquid-crystalline thin films. Another approach is to form chemical gels of liquid crystal molecules with low molecular weight by construction of a polymer network. This method has been investigated for the stabilization of ferroelectric liquid crystal displays. Guymon et al. reported that a polymer network produced by photochemical cross-linking accumu-... 

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