•Understanding the influence of side chain length or structure on the properties of isoindigo based conjugated polymers.•The alkyl side chains on isoindigo unit have no effect on the optical properties of individual molecules.•Alkyl side chains have a significant impact on a series properties of the polymers in the aggregated state.•Hexyl-decyl substituted isoindigo based polymer has the best performance.A series of donor-acceptor (D-A) conjugated polymers based on benzo[1,2-b:4,5-b’]dithiophene (BDT) and isoindigo with different alkyl side chains were designed and synthesized. These polymers named PBDT-TT-IIDO, PBDT-TT-IIDEH, PBDT-TT-IIDBO, PBDT-TT-IIDHD, and PBDT-TT-IIDOD have different length or structure of the alkyl side chains on isoindigo unit. As the length of the alkyl chain increases, the solubility of the polymer enhances. The results indicate that the alkyl side chains have little effect on the optical properties of individual polymer molecules, but have a significant impact on optical, electrochemical, film-forming and photovoltaic properties of the polymers in the aggregated state. PBDT-TT-IIDHD with a sixteen carbon branched chain achieves the best power conversion efficiencies (PCEs) of 6.83% when blending with [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as acceptor. The influence of the alkyl side chain on the short-circuit current is much greater than that of the open circuit voltage. Atomic force microscopy (AFM) reveals that the side chains changed the morphology of the active layers and the size of the phase region. For isoindigo based polymers, hexyl-decyl group in the commonly used alkyl chains appear to be a good choice.Understanding the influence of side chain length and structure on the properties of isoindigo based conjugated polymers.Download high-res image (182KB)Download full-size image

Stimuli-responsive hydrogels are soft, biocompatible and smart biomaterials; however, the poor mechanical properties of the hydrogels limit their application. Herein, we prepared a reductant- and light-responsive polyurethane hydrogel which was made of polyethylene glycol, 1,6-diisocyanatohexane, azobenzene, cyclodextrin and disulfide. Attenuated Total Reflectance Infrared Spectra and 1H NMR were used to characterize the structure of the hydrogel. The hydrogel has a high elasticity (a tensile modulus of 36.5 ± 0.5 kPa and a storage modulus of 52.9 ± 1.2 kPa) at a high water content (91.2 ± 0.4%). Swelling, mechanical and rheological properties of the hydrogel can be tuned by the content of the crosslinker, light and reductant. The hydrogel has low cytotoxicity and it can be used for drug delivery. Ultraviolet irradiation helped to load drugs and the reductant accelerated the drug release. With its high mechanical properties and light- and reductant-responsiveness, the hydrogel is hopefully to be used as a drug carrier.

A novel thermo- and light-responsive random copolymer poly(o-nitrobenzyl methacrylate)-co-2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate (P(NBMA-co-MEO2MA-co-OEGMA)) was synthesized by atom transfer radical polymerization (ATRP). This amphiphilic random copolymer self-assembled into spherical micelles with a PNBMA core and a PMEO2MA/POEGMA corona in aqueous solution. Aggregates were formed when the temperature increased above the lower critical temperature (LCST). Upon UV irradiation, the transformation of hydrophobic PNBMA into hydrophilic poly(methacrylic acid) (PMAA) induced the disruption of the initial micelles and the release of the encapsulated fluorescent dye, Nile Red, into water. The accordingly obtained hydrophilic random copolymer P(MAA-co-MEO2MA-co-OEGMA) exhibited thermo- and pH-responsive behavior. Further increasing the temperature or decreasing the pH, P(MAA-co-MEO2MA-co-OEGMA) formed PMEO2MA/POEGMA-core or PMAA-core micelles with the re-encapsulation of Nile Red. This random copolymer has great potential in applications such as controlled release and selective encapsulation.

Alkyne-functionalized polyhedral oligomeric silsesquioxane was successfully prepared using the commercially available propargylic acid precursor through DCC coupling, and it was further used to modify PEG-b-PCL via click chemistry, resulting in a successful synthesis of POSS grafted PEG-b-PCL block copolymer. The structures of the samples were comprehensively confirmed by FTIR, 1H NMR, GPC and electrospray ionization mass spectrometry (ESI-MS). The thermal properties of the polymers were investigated via DSC. The copolymers with grafted POSS showed excellent thermal properties with an increase of approximately 100 °C in melting temperature compared with the neat PEG-b-PCL. Furthermore, the side group POSS with high crystallinity inducing ability acted as a physical crosslinking point and a thermal enhancement agent and effectively induced the ordered phase separation, giving rise to nanostructures with high parallelism and a smooth interface.

Stimuli-responsive hydrogels are soft, biocompatible and smart biomaterials; however, the poor mechanical properties of the hydrogels limit their application. Herein, we prepared a reductant- and light-responsive polyurethane hydrogel which was made of polyethylene glycol, 1,6-diisocyanatohexane, azobenzene, cyclodextrin and disulfide. Attenuated Total Reflectance Infrared Spectra and 1H NMR were used to characterize the structure of the hydrogel. The hydrogel has a high elasticity (a tensile modulus of 36.5 ± 0.5 kPa and a storage modulus of 52.9 ± 1.2 kPa) at a high water content (91.2 ± 0.4%). Swelling, mechanical and rheological properties of the hydrogel can be tuned by the content of the crosslinker, light and reductant. The hydrogel has low cytotoxicity and it can be used for drug delivery. Ultraviolet irradiation helped to load drugs and the reductant accelerated the drug release. With its high mechanical properties and light- and reductant-responsiveness, the hydrogel is hopefully to be used as a drug carrier.