Multifunctional acrylic oligomers

Novel difunctional acrylic monomers and multifunctional acrylic oligomers with a propensity for intra-intermolecular addition polymerization (cyclopolymerization) have been conveniently synthesized from conventional acrylates or diacrylates and paraformaldehyde under neat conditions using l,4-diazabicyclo[2,2,2]octane (DABCO) as the catalyst (7-5). 

DePass LR, Maronpot RR, Weil CS Dermal oncogenicity bioassays of monofunctional and multifunctional acrylates and acrylate-based oligomers. 7 Toxicol Environ Health 16 55-60... 

A typical UV-cured coating has three or sometimes four main ingredients (1) a multifunctional acrylate monomer, (2) a reactive oligomer, (3) possibly a monoacrylate as reactive diluent, and (4) a photoinitiator (Table 2.20). 

As these reactive oligomers have a high viscosity, they are diluted with a multifunctional and if necessary a monofunctional acrylate monomer. The acrylate monomers reduce the viscosity of the mixture for easier application on substrates. The multifunctional acrylate monomers increase the crosslink density the monofunctional monomers decrease it. 

The main reason for the limited industrial application of radiation-induced cationic polymerization is that oligomers that offer high cure rates are not commercially available. So far, due to their excellent combination of chemical, physical and electrical properties, only multifunctional epoxy oligomers have been used, but these have poor cure speeds compared to acrylate based systems. This is a serious limitation. Interesting alternatives to the epoxys are oligomers based on highly reactive vinyl ethers (21. 22) and the recently developed distsrrene ethers (23). which are as reactive as vinyl... 

Figure 3. Synthesis of ethylene oxide-based multifunctional acrylic vinyl oligomers.

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. ... 

The inks used in silk screening consist of multifunctional acrylics, which act as diluents until the reaction, and acrylated oligomers, which are cross-linked through UV light, which activates the photoinitiator in the ink. As far as we know, three reports of contact dermatitis in silk-screen printers have been reported in the literature. The first case was published in 1986 by Nethercott and Nosal. Their female patient reacted to the UV-curable ink TPGDA, as did our patient, and also to pentaerythritol triacrylate (PETA). 

Radiation cure coatings are typically solvent-free, high sohds systems based on acrylated epoxy or urethane oligomers and diluent multifunctional acrylate monomers. Since radiation intensity varies significantly with... 

The photoinitiated addition of a multifunctional thiol to a difunctional monomer or oligomer gives a crosslinked polymer. The most widely used multifunctional thiol is pentaerythritol tetramercaptopropionate. Ene-monomers can be styrene, acrylates, vinyl ethers, allylic oligomers, etc. For example ... 

The photosensitive layers of early plates were composed of acrylate/methacrylate and acrylated cellulose acetate mixtures. Other printing plates contained polyamides or nylon derivatives as binders. Generally, printing plates contain a mixture of reactive monomers and multifunctional oligomers (pre-polymers), polymeric binders, and photoinitiators with exceptional cure depth. The original photoinitiators were benzoin derivatives. Later, anthraquinone and other systems were used. 

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