A series of novel substituted acetylene monomers bearing fluorene pendant groups (C13H9COCH2CH2CO-R-CH2CCH, R = NH (IV1), R = O (IV2), R = NHCH(CH3)CONH (IV3), R = NHCH(CH3)COO (IV4)) have been synthesized and subsequently polymerized with [Rh(nbd)Cl]2 as a catalyst to obtain the corresponding polyacetylenes (Poly(IV1–4)). The 1H NMR spectra demonstrated that all the obtained polyacetylenes had high cis-stereoregular structures. The results of CD (circular dichroism) and UV–vis spectra showed that Poly(IV3,4) took a tight helical structure, while Poly(IV1,2) did not. The chiral amino acid units in the side chains of Poly(IV3,4) induced the main chain to form the helical conformation. In addition, owing to the large steric repulsion and π-π interaction between the bulky fluorene groups, Poly(IV3,4) showed good helical stability at various temperatures (− 10–60 °C) and in strong polar solvents. Especially, the CD intensity of Poly(IV3) was enhanced with increasing the solvent polarity. Moreover, Poly(IV1–4) also showed good photoluminescent (PL) properties. The nonconjugated aliphatic spacer and the twisting of the polymer main chain were favorable to improve the PL efficiency.

•A series of novel stable helical poly(N-propargylamides) were prepared.•Poly(V1–3) kept stable helices upon the temperature, solvents and UV irradiation.•The strengthened hydrogen bonding increased the helical stability.•Steric repulsion between bulky substituted azobenzene groups stabilized the helix.•Electrostatic interaction between azobenzene dipoles stabilized the helix.A series of novel N-propargylamides bearing substituted azobenzene pendant groups (RC6H4NNC6H4CONHCH(CH3)CONHCH2CCH, R = CH3CH2N(CH2)2OOC(CH2)3CH3 (V1), R = CH3CH2N(CH2)2OOCCH2NHCOCH3 (V2), R = H (V3)) were synthesized and polymerized with [Rh(nbd)Cl]2 as a catalyst to obtain the corresponding polymers (Poly(V1–3)). The azobenzene chromophores in the side chains of Poly(V1,2) contained bulky electron-donating substituents, while the azobenzene in Poly(V3) did not bear this kind of substituent. The introduction of substituted azobenzene chromophores into the side chains of poly(N-propargylamides) was found to increase the hydrogen bond strength, steric repulsion and electrostatic interactions between the neighboring side chains. These factors worked together to improve the helical stability of poly(N-propargylamides). The solubility of these poly(N-propargylamides) was increased by introducing substituents into the azobenzene chromophores. CD and UV–vis spectra showed that all the poly(N-propargylamides) took the helical structures with predominantly one-handed screw sense, which were tight helices. Furthermore, the unsubstituted azobenzene groups in the side chains of Poly(V3) also arranged to form the helical conformation. The helical structures of Poly(V1–3) remained stable at various temperatures (5–60 °C). Poly(V1,2) exhibited good helicity in polar solvent, which indicated that the bulky substituents, electrostatic and steric repulsion between the adjacent side chains lessened the effect of polar solvent on the hydrogen bonding. The main chains of Poly(V1,3) still kept helical sense after the isomerization of trans-azobenzene to the cis form upon UV irradiation. The helical array of azobenzene side chains in Poly(V3) experienced reversible arrangement–disarrangement upon photoirradiation.

A series of novel N-propargylamides carrying dipole azobenzene chromophores were synthesized and polymerized with [Rh(nbd)Cl]2 catalyst to obtain cis-transoid poly(N-propargylamides). The solubility, thermal stability and conformation of these polymers were also studied. The introduction of valeryl group increased the solubility of this kind of poly(N-propargylamides). All the polymers exhibited a good, thermal stability. CD and UV–Vis spectra showed that poly(N-propargylamide) (Poly(V2b)) took a tight helical structure with predominantly one-handed screw sense. Poly(V2b) exhibited a good stable helical structure at various temperatures (5–60 °C). It also maintained good helicity in polar solvent. The improved helix stability could be attributed to the enhanced hydrogen bonding strength and steric repulsion between the newly designed azobenzene groups. Furthermore, the electrostatic repulsion between the dipole azobenzene chromophores in the side chains improved the helix stability as well. The backbone of Poly(V2b) still kept helical sense after the isomerization of trans-azobenzene to the cis form under UV irradiation.

A series of poly(bisbenzoxazole)s (PBOsV) containing fluorenylidene unit are prepared from 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (BAHPF) and various aromatic or alkene diacids by direct polycondensation. These polymers exhibit improved solubility and good thermal stability. The decomposition temperatures at 10% weight loss of them are above 500 °C. X-ray diffractograms of PBOsV1–5 show that all of them are amorphous. The maximum absorption wavelengths of PBOsV1–5 are blue or red shifted relative to poly(p-phenylene-2,6-benzobisoxazole) (PBO). The bandgaps of PBOsV1–5 are in the range of 2.48–2.98 eV, which widen the tunable range of the optical bandgap. The results of photoluminescence (PL) emission spectra indicate the energy transportation has happened between the fluorenylidene and benzoxazole ring. The emission wavelengths of PBOsV1–5 are blue shifted in contrast to PBO and the emission wavelengths of them are in the region of blue or green light, respectively. The PL quantum yields of them are improved due to the introduction of fluorenylidene group. The results of EPR studies show the intrinsic paramagnetic defects in this class of polymers.

A series of novel rigid poly(bisbenzothiazole-urea)s (PBTUs III) containing bulky pendant groups were synthesized from 2,2-diaminodibenzothiazoles and aromatic diisocyanates conveniently in the mild condition. The inherent viscosity, solubility, thermal stability, morphology, mechanical and photophysical properties of them were investigated and compared in detail. The inherent viscosities were in the range of 0.58–0.73 dL/g. All of the polymers exhibited excellent solubility in various polar organic solvents. They also showed good thermal stability and mechanical properties. The decomposition temperatures at 10% weight loss were in the range of 368–431 °C in nitrogen. All the PBTUs III were amorphous. Tensile strength of PBTUs III showed the range from 85 to 98 MPa. Compared with poly(benzothiazole)s, all the PBTUs III had the larger optical bandgap and lower photoluminescence quantum yields.