Photocurable oligomers

The discussion of active ester synthesis in this review focuses on polymers and copolymers of phenyl acrylates and iV-acryloyloxy tkrivatives as synthetic intermediates . Another interesting application of activated (meth)acrylates is the formation of photocurable oligomers [81]. Polymers and copolymers of activated (meth)acrylates have also been studied as models of macromolecular drug carriers [37, 42], In addition, the chemistry of activated esters is equally... 

Maruyama et al, studied photopolymerization of addition products of multifunctional acrylates and aUcoxysilyl alkyl thiol. Three monomers with multiple (trimethoxysilyl)propylthio groups were prepared by them via Michael addition of the multifunctional acrylates. These were neopentyl glycol diacrylate, trimethylol propane triacrylate, and pentaerythritol tetraacrylate that were reacted with (y-mercaptopropyl)trimethoxysilane. These photocurable oligomers were then UV-irradiated using photo cationic and photo radical initiators. They found that polymerization with photo cationic initiator provided films with a high hardness and mar resistance. ... 

Ariga (45) disclosed developments with CTBN-modified epoxy acrylates which when prepared with other lower molecular weight dicarboxylic acids and select carboxyl-terminated oligopolyesters serve as novel oligomers for photocurable coatings. These systems have low uncured viscosity. In the cured state they possess excellent scratch and crosshatch adhesion, good direct and reverse impacts (duPont impact tester) and pass bending diameters of 2 mm. 

Oligomers As indicated in Table II, functionalized oligomers provide the photocured coating with its basic physical properties. A generalized structure for reactive oligomeric resins or pre-polymers is shown below ... 

NVK is used as a sensitizer of cationic photopolymerization. Cation-ically photopolymerizahle, or photocurable, compositions typically contain monomers or oligomers having the epoxy or the ether functionality, and a photoinitiator. The most commonly used photoinitiators employed for photoinduced cationic ring-opening pol5mierizations are diaryliodon-ium salts, or triarylsulfonium salts. 

Alam, R., Khan, M. A., Khan, R.A. et al. (2008) Study on the physico-mechtmictil properties of photocured chitosan films with oligomer and acrylate monomer. Journal of Polymers and the Environment, 16,213-219. 

Table 8 examines simple photocurable models based on epoxy-acrylate oligomers. Two recipes represent two modification approaches (a) Synthesized CTBN-modified... 

Yang and Schaeffer pointed out that the photocuring industry is interested in liquid oligomers that can form highly flexible films. They suggest using elastomeric liquid polybutadiene with acrylic or methacrylic esters. Such oligomers can be illustrated as follows... 

In a study of polymerization kinetics of photocurable compounds based on an epoxy acrylate oligomer and three analogous diacrylate monomers... 

A flexible print material, which can be developed by a water-based developer, has been commercialized. Flexible print material is a gel that contains a photopolymerizable monomer or oligomer. Upon photocuring, the uncrosslinked portion is removed by a solvent and a print plate is prepared. From both the safety and the environmental standpoints, the trend is to use a water-based developer. To improve development capability, a microgel with a hydrophilic surface is used [26]. The solid property, transportability, and handling are improved as a result of the addition of the microgel. 

A typical formulation of a photocurable composite resin contains four basic components a radical-type photo initiator, an acrylate functionalized oligomer, a reactive diluent and the clay mineral filler. The photoinitiator is usually an aromatic ketone which cleaves into two radical fragments upon UV exposure. The telechelic oligomer consists of a short polymer chain (polyurethane, polyether, polyester) end-capped by the very reactive acrylate double bond. An acrylate monomer is generally used as reactive diluent to reduce the resin viscosity. Figure 7.2 shows some typical compounds used in UV-curable acrylic resins. Different types of phyllosilicates were selected as mineral filler an organophilic clay (Nanomer I-30E from Nanocor), native hydrophilic clays (montmorillonite KIO and bentonite) and a synthetic clay (beidellite). 

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