The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007

The ring‐opening copolymerization of donor–acceptor norbornadiene (D–A NBD) dicarboxylic acid monoglycidyl ester derivatives with D–A NBD dicarboxylic acid anhydride was performed with tetraphenylphosphonium bromide as a catalyst in toluene to produce new norbornadiene (NBD) polyesters containing D–A NBD moieties in the main chain and in the side chain in one step in good yields. The photoisomerization of the D–A NBD moieties in these polyesters proceeded very smoothly to give the corresponding quadricyclane groups. Because these NBD polyesters contained many NBD moieties in the polymer chain, they had the highest capacity for heat storage in the D–A NBD polymers reported so far. The stored thermal energy of the irradiated polyesters was evaluated by differential scanning calorimetry analysis to be approximately 150–190 J/g. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4412–4421, 2005

ABSTRACT:The synthesis and photochemical valence isomerization of polymers containing donor-acceptor type norbornadiene (D-A NBD) residues in both main and side chains, by the polyaddition of 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid diglycidyl ester (D-A NDGE) with terephthaloyl chloride follows by substitution reactions of the resulting polymer with potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-3-methylester-2,5-NBD-2-carboxylate, potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-3-(N,N-dipropylcarbamoyl)-2,5-NBD-2-carboxylate, and potassium 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-3-(N-methyl-Nphenylcarbamoyl)-2,5-NBD-2-carboxylate, respectively. The photochemical valence isomerization of the synthesized poly(ester)s (P-1-P-4, and P-5a-c) was examined in tetrahydrofuran solution or in the film state upon irradiation with a 500-W xenon lamp, and it was found that each photochemical reaction proceeded very smoothly. It was also observed that the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4 0 -bis-(diethylamino)benzophenone (BEBP) as a photo-sensitizer in the film state. The stored thermal energies of the irradiated polymers were evaluated by DSC analysis to be 75-153 J/g. [DOI 10.1295/polymj.37.246] KEY WORDS Donor-Acceptor Type Norbornadiene / Polyaddition / Photochemical Valence Isomerization / Photo-sensitizer / Stored Thermal Energy / The photochemical valence isomerization between norbornadiene (NBD) and quadricyclane (QC) is of great interest as a solar energy conversion and storage system, 1-4 because NBD can convert solar energy into 96 kJ/mol of thermal energy through the strain in QC.Nishikubo et al. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] reported the synthesis of photoreactive polymers containing NBD residues in the main chain or the side chain, and it was observed that the NBD residues in the polymers converted smoothly to form QC ones. These NBD-containing polymers had high stored thermal energies. However, these synthesized polymers were not suitable to applications as a material for solar energy conversion and storage systems, because they did not have strong absorption band into visible region and did not have good durabilities in the reversible photochemical reaction.On the other hand, it is known that donor-acceptor type norbornadiene (D-A NBD) derivatives had absorption band into visible region and converted to the corresponding QC derivatives in high quantum yield. 21,22 Furthermore, Nishikubo et al. [23][24][25][26] synthesized the polymers containing D-A NBD moieties in the main chain or side chain and examined their photo-chemical valence isomerization. It was found that their synthesized polymers had high photochemical reactivities and good fatigues of resistance. [23][24][25][26] Furthermore, it is expected that the thermal storage energies of the polymers increase with increasing the ratio of the NBD moieties.From these backgrounds, in this article, we examined...

Polymers containing trifluoromethyl (CF 3 )-substituted donor-acceptor NBD moieties in the side chain or in the main chain were synthesized by substitution or addition with CF r NBD-carboxylic acid derivatives, or by polycondensation of CFrNBD-dicarboxylic acid derivatives, and the durability of the resulting polymers was examined.Photochemical valence isomerization between norbomadiene (NBD) and quadricyclane (QC) is of interest as a solar energy conversion and storage system, I because photoenergy can be stored as strain energy (about 20 kcal/mol) in a QC molecule (Scheme I). Recently, this photochemical reaction has also been investigated as an optical waveguide utilizing photoinduced refractive index changes 2a . b or as a photochromic system potentially applicable to data storage. 2cTaking these unique characteristics of NBD into account, polymers containing NBD moieties have been investigated. However, the photoreactivity and the fatigue resistance of these polymers were insufficient for practical use as advanced materials. 3 Recently, we reported the synthesis of CF 3 -substituted donor-acceptor NBD (CFrNBD) derivatives which not only absorb visible light efficiently but also exhibit efficient fatigue resistance.4 Therefore; we now synthesized new photoreactive polymers containing CFrNBD moieties.The NBDmonomers, namely, NBD carboxylic acid I and NBD dicarboxylic acid 2, were synthesized from eyclopentanedione derivative 3 as shown in Scheme 1. 5 Polymers containing CFrNBD moieties in the side chain were synthesized according to Scheme 2. 5 The reactions of NBD carboxylic acid I with poly(chloromethylstyrene),3b poly(2-chloroethyl vinyl ether) 3c, and poly(glycidyl methacrylate) 3d proceeded smoothly using tetrabutylammonium bromide as a catalyst in DMF to give the corresponding polymers P·I, P·2, and P-3 in 80,83, and 82% yields, respectively. To P-I, P·2, and P-3, NBD carboxylic acid was found to be introduced in 100,93, and 100% yield, respectively. 6 These results show that CFrNBD moieties could be readily introduced in the side chain of many polymers.Next, we synthesized polymers containing CFrNBD moieties in the main chain as shown in Tables I and 2. 5 Polyamide P-4 was synthesized by polycondensation of the bis(4-nitrophenyl) ester 4, obtained from NBD dicarboxlic acid 2, with trans-I,4-diaminocyclohexane as diamine. 7 The yield and the M n of P-4 were 82% and 17800, respectively. 8 This polyamide was also synthesized from 2 with diarnine using DPPA as condensation reagent; the yield and the M n were 88% and 42,900, respectively. Polyester was synthesized by polycondensation of 2 with diol using hafnium chloride as the Lewis acid catalyst. 9 The yield and the M n of p-s were 82% and 39,300, respectively. On the other hand, when the reaction was canied out using WSCD