Phenylene diacrylates

In the 2,5-DSP(a) and P2VB crystals, the directions of three axes of the polymer coincide with those of the monomer whereas a different type of relative orientation is seen in diphenyl- and diethyl 1,4-phenylene diacrylates (3 OPh and 3 OEt), and dipropyl 1,4-(2-cyano)-phenylene diacrylate (4 OPr). 

In previous studies in the author s laboratory it has become clear that, in most diolefin derivatives, replacement of the oxygen atom of an ester moiety by a sulfur atom is possible without changing the photopolymerizable molecular arrangement, and that all of the thioester derivatives and even mixed crystals of the ester containing a small amount of thioester derivatives of 1,4-phenylene diacrylate (PDA) are photostable (Hasegawa et al., unpublished data). 

The amorphous diacrylate monomers chosen for study were two commercially available monomers, p-phenylene diacrylate (PPDA) and 1,6-hexanediol diacrylate (HDDA) (Polysciences, Inc., Warrington, PA). The liquid crystalline diacrylate studied was 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) (13). Chemical structures of these monomers as well as pertinent physical and LC properties are given in Figure 1. All monomers were used without further purification. The ferroelectric liquid crystal mixture consisted of a 1 1 mixture of W7 and W82 (1) (Displaytech, Boulder, CO). This mixture exhibits isotropic (I), smectic A... 

Figure 1. Chemical structures of the monomers used in this work. Shown are a) p-phenylene diacrylate (PPDA- melting point 89° C), b) 1,6-hexanediol diacrylate (HDDA- melting point 5° C, boiling point 316° C), and c) C6M, a liquid crystalline diacrylate (phase sequence Isotropic - 116° C -> Nematic -> 86° C - Crystalline.)...

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-... 

Bisjak, C.R et al. Novel monolithic poly(phenyl acrylate-co-l,4-phenylene diacrylate) capillary columns for biopolymer chromatography. J. Chromatogr. A. 2007, 1147,... 

A more recent method of inducing SCSC [2+2] photoreactivity involves the use of crystals of nanometer-scale dimensions [70]. The method has been successful for the construction of polymers of 2,5-distyrylpyrazine, as well as methyl p-phenylene-diacrylate. Presumably, the nanoscopic crystal size provides the reactant crystals with enough flexibility to withstand strain induced by the photopolymerization process. 

The fact that isomeric compounds 1,4-bis (p-pyridy 1-3-vinyl) benzene and 1,4-bis (p-pyridyl-4-vinyl) benzene failed to photopolymerize under the same conditions indicates the importance of the topochemical arrangement of the double bonds. This was studied by x-ray analysis of the crystals. Topochemistry has been shown to be important in the case of the dimerization of substituted cinnamic acids 25>. -Phenylene-diacrylic acid and its esters photopolymerize to yield polyesters containing cyclobutane units 26>. 

Table 17. Cholesteric poly(esterimide)s derived from phenylene diacrylic acid and 4-ami-nobenzoic trimellitimide...

A major distinction between the migration of energy in dilute solid solutions of polymers and solid films is that in the former the excitons are restricted to an intramolecular path along the polymer backbone, while in solid films of the neat material, they can migrate intermolecularly from one chain to another. An example of a material that illustrates this distinction rather well is the resist polymer PPDA (11), which is based on the p-phenylene diacrylate chromophore that is described in Chapter 6. 

Subsequently, with the aim of amplifying the chirality created in the system in this first generation step, the effect of the chiral products on the crystallization of the two enantiomeric parent crystals, A and A, was investigated. A number of disubsti-tuted phenylene-diacrylates packing in chiral crystals with the structural motif of Scheme 1 were crystallized, either from the melt or from solution, in the presence of enantiomerically pure dimers, trimers or oligomers generated photochemically from the same phases in a previous step. It was observed in all experiments carried out... 

Another family of diolefins in which a similar reaction was observed is that of phenylene diacrylic acid 2 and its derivatives. These also undergo lattice-controlled polymerization, and the very close relationship between the packing of the diacrylic acids, cinnamic acid, and DSP is shown in Figure 6.1. 

Suzuki, R, Suzuki, Y, Nakanishi, H., and Hasegawa, M., Four-center photopolymerization in the solid state polymerization of phenylene diacrylic acid and its derivatives, J. Polym. ScL, Al, 2319, 1969. 

Nakanishi, H., Ueno, K., and Sasada, Y, The crystal and molecular structure of /7-phenylene diacrylic acid diethyl ester, Acta Cryst., B34, 2209, 1978. 

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