Methacrylate groups

A recent addition to Table 3, Reactive Blue 246 differs from the other dyes and is not added to a finished lens. The dye molecule has methacrylate groups attached to an anthraquinone and is incorporated directiy into the polymer matrix during polymer cure (175). This in-monomer concept has the potential to reduce dramatically the cost of visibiUty tinting of a contact lens. 

Acrylic and methacrylic acids and their esters are highly versatile materials in that the acid and ester side groups can partake in a variety of reactions to produce a very large number of polymerisable monomers. One particularly interesting approach is that in which two methacrylic groupings are linked together so that there are two, somewhat distant, double bonds in the molecule. In these cases it is possible to polymerise through each of these double bonds separately and this will lead eventually to a cross-linked network structure. 

Hybrid systems of acrylics with other technologies have been reported. Aciylic and epoxy polymers can be coupled through the use of 2-methacryloloxyethyl phosphate. The phosphoric acid functionality reacts with epoxy and the methacrylate group copolymerizes with the acrylic backbone [ 145] (Scheme 14). 

They too obtained a product which was poorly soluble in THF and many other solvent combinations. Acidification with HC1 in THF improved the solubility, but the product displayed an IR band at 1730 cm"1 in addition to a methacrylic acid at 1700 cm"1. They attributed the band at 1730 cm"1 to unreacted isobutyl methacrylate groups, but in light of our observations, it may be due to the same type of side-reaction. 

The photoinduced radical crosslinking of silicone containing pendant acrylate 1 and 3 or methacrylate groups 2 and 4 was investigated by swelling and calorimetric measurements. 

Another way for covalent immobilisation is to synthesise indicator chemistry with polymerizable entities such as methacrylate groups (Figure 4). These groups can then be copolymerized with monomers such as hydrophobic methyl methacrylate or hydrophilic acryl amide to give sensor copolymers. In order to obtain self-plasticized materials, methacrylate monomers with long alkyl chains (hexyl or dodecyl methacrylate) can be used. Thus, sensor copolymers are obtained which have a Tg below room temperature. Similarly, ionophores and ionic additives (quaternary ammonium ions and borates) can be derivatised to give methacrylate derivatives. 

Figure 4. Synthesis of an indicator dye for amines which exhibits methacrylate groups for preparation of copolymers. The dye shows a reversible change in fluorescence from green to blue upon interaction with amphetamine.

Synthesis. Functionalized monomers (and oligomers) of sebacic acid (SA-Me2) and 1,6 -bis(/ -carboxyphenoxy)hexane (CPH-Me2) were synthesized and subsequently photopolymerized as illustrated in Figure 1. First, the dicarboxylic acid was converted to an anhydride by heating at reflux in methacrylic anhydride for several hours. The dimethacrylated anhydride monomer was subsequently isolated and purified by dissolving in methylene chloride and precipitation with hexane. Infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis results indicated that both acid groups were converted to the anhydride, and the double bond of the methacrylate group was clearly evident. 

It has been shown that polymers with free phthalic acid groups dissolve much faster and at a lower pH than those esterified with acrylic or methacrylic groups. The presence of plasticizer and the nature of the salts in the dissolution medium influence the dissolution rate [62],... 

The third case is the copolymerization of a monomer A with the diene BC where groups A and B have equal reactivity, but group C has a much lower reactivity. An example of such a case would be methyl methacrylate-allyl methacrylate, where A and B are the two methacrylate groups and C is the allyl group. If r is the reactivity ratio between the C and B groups, then the following hold for the radicals derived from the A and B groups ... 

Table 5.2 Reactivity ratios for copolymerization of p-cresyl formaldehyde oligomers with methacrylic groups (10) and styrene (2). [Reproduced from S. Polowinski, Polimery, 39, 419 (1994), with kind permission from 1. Ch. P.]...

The copolymerization within a wide range of initial compositions of the monomer mixtures was carried out in DMF solution in the presence of AIBN labeled with C. The residual unsaturation (molar ratio of the unsaturated pendant methacrylate groups to the total methacrylate groups linked with the template chain in the copolymer) is rather low (from 0.01 to 0.08). Also, a number of branching points can be estimated at 1-2 per hundred repeating units. These results confirm the conclusion that propagation occurs... 

After hydrolysis by 2N methanol solution of H2SO4, the product was neutralized with KOH to pH=5 and methanol evaporated. The dry residue was expected to be poly(allilamine), polymethacrylic acid, and K2SO4. Indeed, after extraction with anhydrous methanol and acetone, poly(allilamine) was identified by NMR and IR spectrometries. After evaporation, solvent from the methanol part of the extract insoluble in chloroform part was obtained. After esterification by diazomethane the product was identified as polyfmethyl methacrylate) on the basis of IR and H-NMR spectroscopy. IR spectroscopy was applied in order to examine the copolymerization of multimethacrylate (p-cresyl-formaldehyde oligomers with methacrylic groups) with st3rrene. It was found that double bond peak at 1650 cm disappeared during the process and it was absent in the product of polymerization. Polymerization and... 

Polyurethane hydrogels derived from UV curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well-defined hard segments centered with a polyether-based soft segment and end-capped with methacrylate groups. The hydrophilic monomers studied were 2-hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris(trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All compositions were UV... 

A polystyrene with a functionality such as a methacrylate group copolymerized with a mixture of ethyl and butyl acrylate should yield a graft structure meeting the criteria of a thermoplastic elastomer as shown in Figure 13. The data in this figure show that as the MACROMER content is increased, the tensile... 

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