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The ring-expansion reaction of equimolar cyclic dithioester 1 with 3-phenoxypropyrene sulfide (PPS) (cyclic dithioester 1/PPS = 1/2) was examined in the presence of TBAC as a catalyst in NMP for 24 h. It was found that intermolecular ester-exchange reaction occurred during the insertion reaction of PPS into cyclic dithioesters, and cyclic polymers with Mns = 3600−8900 were obtained in 80−96% yields. The structures of the obtained cyclic polymers were confirmed by the ¹H NMR, ¹³C NMR IR, and MALDI TOF-MS spectroscopy. The continuous insertion reaction of excess PPS into cyclic dithioester (cyclic dithioester 1/PPS = 1 /50) was also examined, and it was found that the insertion reaction proceeded quantitatively to afford the corresponding cyclic polysulfide with Mn = 42 000 and Mw/Mn = 4.50 in a 96% yield.

Polymers containing trifluoromethyl (CF3)-substituted donor−acceptor NBD moieties in the side chain or in the main chain were synthesized by substitution or addition of a CF3−NBD−carboxylic acid derivative or by polycondensation of a CF3−NBD−dicarboxylic acid derivative. The photoisomerization of the NBD moieties in these polymers proceeded very smoothly to give the corresponding QC moieties. Furthermore, the NBD moieties exhibited efficient fatigue resistance.

The synthesis of poly(carbonate)s with phenoxymethyl groups in their side chains by a polyaddition of bisphenol A diglycidyl ether (4a) with diphenyl carbonate (2) using quaternary onium salts or crown ether complexes as catalysts is described. When the polyaddition was performed with the catalyst containing Cl^- as a counteranion such as tetrabutylammonium chloride, tetrabutylphosphonium chloride, or 18-crown-6/KCl without solvent at 100 °C for 48 h, the corresponding poly(carbonate) with high molecular weight (Mn = 20 000−34 000) was successfully obtained. ¹H NMR and ¹³C NMR spectra of the resulting polymer indicated that the reaction proceeded regioselectively at the epoxy groups of 4a to give the polycarbonate with pendant phenoxy groups. The polyaddition of various bis(epoxide)s with 2 also proceeded in bulk to provide the corresponding poly(carbonate)s with high molecular weight in good yield.

Polyesters containing donor−acceptor norbornadiene (D−A NBD) residues in the main chain were synthesized by the polyaddition of D−A NBD dicarboxylic acids, 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid and 5,6-bis(4-methoxyphenyl)-7,7-dimethyl-2,5-norbornadiene-2,3-dicarboxylic acid, with bis(epoxide)s. The photoisomerization of the NBD residues in the resulting polyesters proceeded smoothly to give the corresponding quadricyclane (QC) groups. The NBD residues in these polyesters showed resistivity to repeated cycles of the interconversion.

The polyaddition of bisphenol A diglycidyl ether (4a) with 2,2‘-bis[(4-chloroformyl)oxyphenyl]propane (5) was examined using quaternary onium salts as catalysts. When the polyaddition was performed using catalysts containing Br^- as a counteranion such as tetraphenylphosphonium bromide in chlorobenzene at 100 °C for 48 h, the corresponding poly(alkyl aryl carbonate) with high molecular weight (Mn = 59 000) was obtained. It was found from the ¹H NMR and ¹³C NMR spectra of the obtained polymer that the reaction proceeded regioselectively at the epoxy group of 4a to provide the polycarbonate with pendant chloromethyl groups. The polyaddition of various bis(epoxide)s with 5 also proceeded smoothly to give the corresponding poly(carbonate)s with high molecular weight in good yields. The chemical modification of the obtained poly(carbonate)s with pendant chloromethyl groups by the phase-transfer method was also investigated using nucleophiles such as potassium thiocyanate and potassium 3-phenyl-2,5-norbornadienecarboxylate.

Six trimers with biphenyl mesogenic groups and polymethylene spacers were synthesized. From these trimers and biphenol diglycidyl ether (BPGE), a new series of combined liquid crystalline polymers (LCPs) with polyether backbone were synthesized by the polyaddition with quaternary phosphonium chloride as catalyst. The effects of flexible spacer length on the phase transition and mesomorphism of the resulting trimers and combined LCPs were studied using differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. The trimers with 1,3-propylene and 1,4-butylene spacers were absent of mesophase, and the trimers with odd-numbered spacers, 1,5-pentylene and 1,7-heptylene, were nematic. In contrast, the trimers with even-numbered spacers, 1,6-hexylene and 1,10-decylene, were smectic within very narrow temperature ranges. All the combined LCPs were thermotropically nematic, though the crystalline behavior was complex with varying side-chain spacer length. The combined LCPs with 3, 5, and 10 methylene units (n) of side-chain spacers were semicrystalline at room temperature while other polymers were glassy. The combined LCPs showed general odd−even effects of side-chain length on TCP and isotropization entropy in which the polymers with even numbers of methylene units in side-chain spacer showed higher values.

Novel sequence-ordered poly(S-alkyl thioester)s were synthesized on the basis of transformation of a backbone of the poly(S-aryl thioester) (P-1) using the regioselective insertion of thiiranes. The insertion reaction of 3-butoxypropylene sulfide (BPS) into P-1 using catalysts such as tetrabutylammonium chloride (TBAC), tetrabutylphosphonium chloride, or 18-crown-6-ether/potassium chloride in DMAc at 70 °C for 6 h proceeded completely and regioselectively to provide an ordered poly(S-alkyl thioester) (P-2a) with a new sequence. The molecular weight of P-2a was reasonably higher than that of the starting polymer P-1. The structure of P-2a including a head-to-tail sequence of BPS unit was well-characterized by IR, ¹H NMR, ¹³C NMR spectroscopies, GPC, and elemental analysis. Various sequence-ordered poly(S-alkyl thioester)s were successfully synthesized by the insertion reaction of 3-phenoxypropylene sulfide, BPS, or cyclohexene sulfide using the TBAC catalyst under the same conditions. It was demonstrated that the transformation of the polymer backbone because of the regioselective insertion of thiiranes using quaternary onium salts was a useful method for achieving the synthesis of sequence-ordered polymers.