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A novel triazole-cored, star-shaped, conjugated molecule (TDGTPA) has been synthesized for use as an electron-selective interlayer in inverted polymer solar cells (PSCs). This star-shaped molecule comprised a triazole unit as the central core, 2,5-thienyl diketopyrrolopyrrole units as π-conjugated bridges, and tert-butyl-substituted triphenylamine units as both end groups and donor units. The inverted PSC had the device structure indium tin oxide/ZnO/TDGTPA/poly(3-hexylthiophene) (P3HT)/fullerene derivative (PC71BM)/MoO3/Ag. Inserting TDGTPA as the electron-selective layer enhanced the compatibility of the ZnO-based electron transport layer and the P3HT:PC71BM blend-based photoactive layer. The low energy of the lowest unoccupied molecular orbital (−3.98 eV) of TDGTPA was favorable for electron transfer from the photoactive layer to the ZnO layer, thereby enhancing the photovoltaic performance of the PSC. The photo-conversion efficiency of the device incorporating TDGTPA as the electron-selective layer was 15.8% greater than that of the corresponding device prepared without it.

A spirobichroman dianhydride (SBCDA) was prepared through oxidation of an octamethyl spirobichroman (OMSBC), which was synthesized from acid-fragmentation of bisphenol A by 3,4-dimethylphenol, followed by Diels–Alder reaction. The reaction mechanism was proposed, and the optimal reaction conditions were discussed. Based on a high temperature solution polymerization of SBCDA and 4,4′-diaminodiphenylmethane (DDM), a spirobichroman-containing polyimide, SBC-DDM, was successfully prepared. Because of the contorted spiro-structure and rigid polymer backbone, SBC-DDM exhibits a large free volume, leading to outstanding organo-solubility and a low dielectric constant. In addition, the resulting film of SBC-DDM shows foldability, a high glass transition temperature, and good thermal stability.

Polythiophenes (PTs) featuring di(ethylene glycol)-substituted 2,5-thienyl diketopyrrolopyrrole (DG-TDPP) moieties as conjugated units in the polymer backbone and tert-butyl-substituted triphenylamine (tTPA)-containing moieties as pendant units have been synthesized through Stille coupling. Incorporating the electron-deficient DG-TDPP moieties within the polymer backbone and appending the tTPA units promoted charge balance and efficient conjugation within the extended conjugated frameworks of the polymers, resulting in lower band gap energies and red-shifting the maximum UV-Vis absorption wavelength. The influence of the DG-TDPP content on the optical, electrochemical, and photovoltaic (PV) properties of the polymers has been studied. Incorporating a suitable content of DG-TDPP moieties in the polymer backbone enhanced the solar absorption ability and conjugation length of the PTs. The PV properties of bulk-heterojunction solar cells based on PT/fullerene derivatives improved after incorporating DG-TDPP units in the backbones of the side chain-conjugated PTs.

To study the co-reaction of benzoxazine and triazine, a triazine-containing benzoxazine (P-tta) was prepared through nucleophilic substitution of 4-(2H-benzo[e][1,3]oxazin-3(4H)-yl)phenol (P-ap) with 2,4,6-trichloro-1,3,5-triazine. DSC thermograms show that the exothermic temperature of P-tta is lower than that of other benzoxazines with a similar structure except for the triazine structure, so we speculate that the forward polymerization is related to the existence of the triazine structure. Through monitoring the curing process using IR, we propose that the curing reactions of P-tta include a concerted co-reaction between the triazine and benzoxazine, and a self-polymerization of benzoxazine. A thermoset with a high Tg (279 °C, DMA data), a low thermal expansion coefficient (32 ppm per °C), and high thermal stability (Td5% 417 °C) can be obtained through the curing of P-tta.

A polybenzoxazine precursor, P(BF-bapp)-1, was prepared through a strategy of A–A and B–B polycondensation. The A–A monomer is 5,5′-methylenebis(2-hydroxybenzaldehyde), and the B–B monomer is 2,2-bis[4-(4-aminophenoxy)phenyl] propane (BAPP). The inherent viscosity (at 0.5 g dL−1 in NMP) of P(BF-bapp)-1 is as high as 0.34 dL g−1, which is higher than that (0.23 dL g−1) of a structurally similar polybenzoxazine precursor, P(BF-bapp)-2, that was prepared through traditional Mannich condensation of BAPP/bisphenol F/paraformaldehyde. A third structurally similar polybenzoxazine precursor, P(BF-bapp)-3, with an inherent viscosity of 0.09 dL g−1, and a phenol and BAPP-based benzoxazine monomer, P-bapp, were prepared for properties comparison. After thermal curing of the benzoxazines, we found that a benzoxazine thermoset based on a high molecular weight precursor has advantages in higher Tg, higher char yield, lower refractive index (low dielectric constant according to Maxwell's equation), and better mechanical properties. The results demonstrate the robustness of a polybenzoxazine precursor prepared through a strategy of A–A and B–B polycondensation, which has never been reported in the benzoxazine field.

A series of hydrogen bond-rich poly(urea/malonamide) dendrons were utilized as surfactants to facilitate the formation of honeycomb-like porous structures from the breath figure (BF) process. With the addition of a small amount of dendritic surfactants to polymers such as poly(D,L-lactide), polystyrene or poly(methyl methacrylate), a well-organized honeycomb-like surface could be achieved. These uniform porous arrays from the BF method with free-standing capacity benefit from the support of their polymer matrices without resorting to a painstaking polymerization process to provide bulky dendritic side-chain polymers. The formation of water-driven honeycomb-like surfaces was also dependent on the concentration of surfactants in a polymer matrix, apart from the chemical structure. Furthermore, a quantitative analysis of the interfacial tensions between water and polymer solution revealed a dynamic procedure of water droplets stabilized by the surfactants on the as-cast polymer films during the solvent evaporation step of the BF method. Among all these dendritic surfactants, the dendrons with one or two hydroxyl groups at the focal point and plenty of octadecyl groups in the periphery exhibited an amphiphilic nature, and were able to create well-balanced interfacial tensions capable of maintaining water in droplets. Consequently, this type of dendron as a surfactant can be blended with a wide range of polymers to create regular honeycomb-like arrays.

A linear-dendritic block copolymer (LDBC) functionalized exfoliated graphene nanosheets (XGS)/silver nanoparticles (AgNPs) was prepared for using as the interfacial layer between the zinc oxide (ZnO) based electron-selective layer and poly(3-hexylthiophene) (P3HT)/fullerene derivative (PC61BM) blend based photoactive layer in an inverted polymer solar cell (PSC). The LDBCs were prepared by the respective addition reaction of a hydrophilic poly(oxyalkylene)amine with hydrophobic dendrons of various generations based on 4-isocyanate-4′-(3,3-dimethyl-2,4-dioxo-azetidine)-diphenylmethane (IDD). The dendrons having polyurea/malonamide functionalities were synthesized by using IDD as a building block. Moreover, the dendrons comprised not only hydrogen bond-rich malonamide linkages, but long alkyl chains at the peripheries as well. XGS were respectively grafted with these amphiphilic LDBCs to afford XGS-dendritic derivatives (XGS-G0.5, XGS-G1.5, and XGS-G2.5). Subsequently, a nanohybrid, XGS-G2.5/AgNPs was obtained through the reduction of Ag+ on the surface of LDBC modified XGS. The dendrons would serve as the effective templates for hosting AgNPs. By the incorporation of XGS-G2.5/AgNPs nanohybrid, it rendered the PSC an increased power conversion efficient (PCE) to 4.04%, a 19.5% improvement over a PCE of 3.38% for the bare inverted PSC, due to the localized surface plasmon resonance of AgNPs, and the improvement of compatibility and charge transfer capacity between ZnO based cathode and photoactive layer.