Photocrosslinkable

The photografting and photocrosslinking processes in which the photoinitiation is carried out by pre-existing polymer in the presence of vinyl monomer. The pre-existing polymer may itself be photoactive or, with the presence of photoinitiator, can interact with a polymer to produce a radical on the backbone of the polymer chain. 

When these polymers are subjected to light of A = 365 nm in bulk vinyl monomer, (MMA or styrene) grafted or extensive crosslinking polymers were produced. The photografting or photocrosslinking occurs through the macro-radicals photochemically generated on the backbone of the polymer ... 

Bryant, S.J. and Anseth, K.A., The effects of scaffold thickness on tissue engineered cartilage in photocrosslinked poly(ethylene oxide) hydrogels. Biomaterials, 22, 619-626, 2001. 

N. T., Lhomme J., Helene C. Sequence-specific recognition, photocrosslinking and cleavage of the DNA double helix by an oligo-[alpha]-thymidylate covalently linked to an azidoproflavine derivative. Nucleic Acids Res. 1987 15 7749-7760. 

When the substituent groups in the polyphosphazenes were azobenzene [719] or spiropyran [720] derivatives, photochromic polymers were obtained, showing reversible light-induced trans-cis isomerization or merocyanine formation, respectively. Only photocrosslinking processes by [2+2] photo-addition reactions to cyclobutane rings could be observed when the substituent groups on the phosphazene backbone were 4-hydroxycinnamates [721-723] or 4-hydroxychalcones [722-724]. 

Hydroxy Benzophenone 4-Hydroxy Benzophenone Hydrogen Abstraction Processes Photocrosslinking ... 

Hydroxy Benzophenone N(CH3)2 3-N,N -Dimethylamino Phenoxy Electron Abstraction, Followed by Proton Migration Photocrosslinking" ... 

In order to learn more about the photocrosslinking process, we synthesized 1,1-bis(trimethylsiloxy)-1-phenyl(trimethyl)disilane (5) as a model compound and examined its photochemical behavior in solutions. Compound 5 could readily be prepared by cohydrolysis of 1,1-dichloro-1-phenyl(trimethyl)disilane with a large excess of chloro-trimethylsilane in high yield. 

All of the photocrosslinking described here begin with surface of the films. The photocrosslinking leading to the solid films under a nitrogen atmosphere would proceed by the mechanism analogous... 

The first published crystal structure of the full length HHR [126] in which there was no solvent or ions resolved showed A9 and the scissile phosphate in close proximity, consistent with the interpretation of thio effect measurements [130], and the G8 02 and G12 Ni poised to act as a general acid and base, respectively, as proved in previous photocrosslinking [131] and mutation experiments [132], Given the strong evidence that Mg2+ participates directly in the catalytic process together with the spatial proximity of the A9 and scissile phosphate, made the placement of an Mg2+ ion in bridging position a reasonable assumption. 

Tsafack V.C., Marquette C.A., Pizzolato F., Blum L.J., Chemiluminescent choline biosensor using histidine-modified peroxidase immobilized on metal-chelate substituted beads and choline oxidase immobilized on anion-exchanger beads co-entrapped in a photocrosslinkable polymer, Biosens. Bioelectron, 2000 15 125-133. 

Chou Al, Nicoll SB (2009) Characterization of photocrosslinked alginate hydrogels for nucleus pulposus cell encapsulation. J Biomed Mater Res A 91(1) 187-194... 

Reza AT, Nicoll SB (2009) Characterization of novel photocrosslinked carboxymethyl-cellulose hydrogels for encapsulation of nucleus pulposus cells. Acta Biomater 6(1) 179-186... 

Photocrosslinking. The second class of photopolymer chemistry that is used in some commercial products is based on the reaction of unsaturated moieties attached to an organic polymer. These photopolymer materials include the [2+2] cycloaddition of the ethylenic groups in poly(vinyl cinnamate) polymers and in the newer styryl pyridinium (10) and thiazolium (77) derivatives of poly(vinyl alcohol). The main advantage of this chemistry is that, unlike free-radical photopolymerization, they are insensitive to the presence of oxygen. This photopolymer mechanism is principally used in applications employing a washout development process (e.g. resists). 

The aryl azido derivatives of [32P]NAD+ were employed to site-specifically incorporate photoactivatable ADP-riboses to transducin at Cys-347 by means of pertussis toxin, and the conjugation was followed by irradiation. Photocrosslinking revealed three major bands after irradiation which corresponded to a-y(47 kDa), a-a (83 kDa),and a-a-a (105kDa) subunit contact domains [88]. 

A number of new resist materials which provide very high sensitivities have been developed in recent years [1-3]. In general, these systems owe their high sensitivity to the achievement of chemical amplification, a process which ensures that each photoevent is used in a multiplicative fashion to generate a cascade of successive reactions. Examples of such systems include the electron-beam induced [4] ringopening polymerization of oxacyclobutanes, the acid-catalyzed thermolysis of polymer side-chains [5-6] or the acid-catalyzed thermolytic fragmentation of polymer main-chains [7], Other important examples of the chemical amplification process are found in resist systems based on the free-radical photocrosslinking of acrylated polyols [8]. 

The use of phenolic polymers in photocrosslinkable systems usually involves multicomponent systems which incorporate polyfunctional low molecular weight crosslinkers. For example, Feely et al. [9] have used hydroxymethyl melamine in combination with a photoactive diazonaphthoquinone which produces an indene carboxylic acid upon irradiation to crosslink a novolac resin. Similarly, Iwayanagi et al. [10] have used photoactive bisazides in combination with poly(p-hydroxy-sty-rene) to afford a negative-tone resist material which does not swell upon development in aqueous base. 

Constantinos G. Tsiafoulis et al. report the electrochemical behaviour of a composite film based on ferrocene intercalated V205.nH20 xerogel (FeCp2-VXG) with photocrosslinkable polyvinyl alcohol with styrylpyridinium residues (PVA-SbQ), in order to be used as an electrocatalyst and host protein platform to develop an amperometric biosensor. 

It is known that aromatic azides are photodecomposed to give active nitrenes as the transient species, which react with the environmental binder polymers to crosslink them. However, the mechanism of these photocrosslinking polymers has not been studied in detail. L.S.Efros et al. have proposed that the rubber polymer is crosslinkes in such a way that the aromatic nitrene inserts into an unsaturated bond of the polymer to give an aziridine ring. The experimental evidence for this, however, has not been given (8). 

In the present experiment, we have studied the mechanism of photocrosslinking of 1,2-polybutadiene by aromatic azide, based on the reaction of aromatic nitrene with unsaturated hydrocarbon monomeric compounds. 

Table 2. Photolysis and Biodegradation of Polymers that Undergo Primary Photocrosslinking.

Azidophenylalanine can also be used for photocrosslinking, which will be discussed in Section 5.18.3.3.1. 

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