•BAPC has good miscibility with plasticizer DAP.•The phase transition diagram of BAPC/DAP blends with DCP as initiator during heating has been constructed.Bisphenol-A polycarbonate (BAPC) is an important engineering plastic with superior optical and mechanical properties, but it is difficult to be processed due to the high melt viscosity. In this work, the blends of BAPC and reactive plasticizer of diallyl phthalate (DAP) were studied before and after polymerization of DAP using dicumyl peroxide (DCP) as thermal initiator. The morphology evolution and phase transitions of the blends during heating were investigated by polarized optical microscopy equipped with hot stage and differential scanning calorimetry. With raising temperature, the apparent phase transitions, i.e., thermally induced partial phase separation with upper critical solution temperature (UCST) behavior, BAPC cold crystallization, DAP polymerization and BAPC crystal melting, occurred in sequence. Compared to pure BAPC, the BAPC/poly(DAP) blends with 10–15 wt.% of poly(DAP) had good performances, including similar glass transition temperature, tensile strength and ∼80% of optical transmittance in the wavelength range of 600–800 nm, as well as an increase of 64–68% for moduli and 100–135% for melt flow index, respectively. These good performances were attributed to the bicontinuous structure of the blends. This study provides a facile strategy to realize the easy processing for intractable polymers and to maintain, even to enhance the high performances of the original polymers.Download full-size image

Ionic liquid plasticized cellulose (IPC) materials were prepared with microcrystalline cellulose (MCC) and 25–70 wt% 1-butyl-3-methylimidazolium chloride (BmimCl) by direct thermal processing. Their chemical, morphological and crystalline structures were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction, and their glass transition behaviors and mechanical properties were discussed. The results show there is no chemical reaction between cellulose and the ionic liquid. BmimCl only acts as a plasticizer to improve the thermal processability of MCC, the IPC materials show only one glass transition terrace and can be processed repeatedly. Based on the free volume transition and the percolation of continuous hydrogen bonding networks, the effects of free volume and H-bonding interactions on the glass transition have been differentiated. Furthermore, the phase diagram with four regions has been plotted for IPC materials, which is useful to optimize the thermal processing and modulate the properties of cellulose materials.

Poly(acrylic acid)/azobenzene microcapsules were obtained through distillation precipitation polymerization and the selective removal of silica templates by hydrofluoric acid etching. The uniform, robust, and monodisperse microcapsules, confirmed by transmission electron microscopy and scanning electron microscopy, had reversible photoisomerization under ultraviolet (UV) and visible light. Under UV irradiation, azobenzene cross-linking sites in the main chain transformed from the trans to cis isomer, which induced the shrinkage of microcapsules. These photomechanical effects of azobenzene moieties were applied to the encapsulation and release of model molecules. After loading with rhodamine B (RhB), the release behaviors were completely distinct. Under steady UV irradiation, the shrinkage adjusted the permeability of the capsule, providing a novel way to encapsulate RhB molecules. Under alternate UV/visible light irradiation, a maximal release amount was reached due to the continual movement of shell networks by cyclic trans–cis photoisomerization. Also, microcapsules had absolute pH responsiveness. The diffusion rate and the final release percentage of RhB both increased with pH. The release behaviors under different irradiation modes and pH values were in excellent agreement with the Baker–Lonsdale model, indicating a diffusion-controlled release behavior. Important applications are expected in the development of photocontrolled encapsulation and release systems as well as in pH-sensitive materials and membranes.

Liquid-crystalline (LC) physical gels with a high modulus and low driving voltage were prepared through the self-assembly of sorbitol derivatives as gelators in a nematic liquid crystal, 4-pentyl-4′-cyanobiphenyl (5CB). The structural difference among the used gelators, i.e. 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS), 1,3:2,4-di-O-p-methylbenzylidene-D-sorbitol (MDBS) and 1,3:2,4-di-O-m,p-dimethylbenzylidene-D-sorbitol (DMDBS), is only the number of methyl groups on their phenyl rings. The phase transition temperature, mechanical and electro-optical properties of three LC gels were systematically investigated. Compared with DBS, MDBS and DMDBS with methyl groups on phenyl rings have higher gelation ability in 5CB. The three LC gels exhibit good self-supporting ability with storage moduli higher than 104 Pa when the gelator content is increased to 1.5 wt%. At 3.0 wt% and a gelator content less than 1.0 wt%, both moduli of MDBS and DMDBS gels are obviously higher than that of DBS gel due to the enhanced reinforcement of the more rigid, thicker nano-fibrils and the formed nano-fibrillar network texture in MDBS and DMDBS gels. Also, the driving voltages of LC gels decrease in the order of DBS, MDBS and DMDBS gels with increase of LC domain size and nano-fibril diameter. For DMDBS gel with 3.0 wt% gelators, the threshold voltage and saturation voltage are only 0.5 and 3.5 V μm−1, showing its potential application in self-supporting light-scattering electro-optical displays.

A facile approach was developed to synthesize conjugated block copolymer (BCP) poly(ethylene oxide)-b-polyaniline (PEO–PANI). Aldehyde group-terminated PEO was prepared by an esterification reaction of p-formylbenzoic acid and PEO and then reacted with PANI from chemical oxidative polymerization. FT-IR, 1H NMR, and GPC results indicated that BCPs with different PEO block lengths were successfully synthesized. Moreover, the BCPs were employed to noncovalently modify multiwalled carbon nanotubes (MWNTs) through either the direct or indirect method. In the former method, transmission electron microscopy images showed that a core–shell MWNT@BCP hybrid with a shell thickness of gyration diameter of PEO block (2Rg,PEO) was obtained in 1-methyl-2-pyrrolidone (NMP). These hybrids can be well dispersed in many common solvents and poly(vinyl alcohol) matrix. With the increase of PEO block length, the stability of the MWNT dispersion would be highly improved. Interestingly, in the indirect method where deionized water was added to the NMP solution of BCP/MWNT mixture, the surface of the hybrid micelles encapsulated with MWNTs changed from smooth into hierarchically thorny with the increase of BCP/MWNT weight ratio. In this case, the water contact angle had a minimum value of ∼70° at the ratio of 1/8, indicating that the hierarchical thorns followed a Cassie–Baxter regime rather than a Wenzel one. A possible formation mechanism of the unique structure was also proposed.

Monodisperse silica particles coated with azobenzene polymer (PAzo) shell were synthesized through distillation precipitation polymerization. Robust PAzo microcapsules were obtained after selective removal of the silica templates by hydrofluoric acid (HF) etching. These PAzo microcapsules, confirmed by transmission electron microscopy (TEM) investigation, had excellent reversible photoisomerization with transformation between trans and cis isomers under ultraviolet (UV) and visible lights. Due to their compatibility with PAzo, acetonitrile would be trapped in the network of the shell during polymerization. Pore channels in the shell, confirmed by nitrogen adsorption–desorption test, would be produced after acetonitrile evaporation. Loading and release of rhodamine B (RhB) molecules in PAzo microcapsules were carried out and indicated that cis azobenzene showed larger pore diameter (named as “open switch”) under UV light which favored permeation of RhB molecules, while trans structure (named as “closed switch”) under visible light slowed down the process. In addition, both release profiles obeyed pure Fickian diffusion with a power law of t0.42. Diffusion coefficient of RhB from PAzo microcapsules under visible light (1.47 × 10−12 cm2/s) was lower than that under UV light (2.12 × 10−12 cm2/s).Structure of pore channels in the shell of PAzo microcapsules and release curves of RhB from PAzo microcapsules.

By means of distillation precipitation polymerization, the silica-hybrid particles with polyazobenzene shell (PAzo@SiO2) microspheres were prepared with 6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate (Azo-M) as monomer, divinylbenzene (DVB) as cross-linker, and ∼250 nm vinylated sol-gel silica particles as template. Hollow polyazobenzene microspheres were further developed after selective removal of the silica cores with HF solution. When the content of DVB related to Azo-M is 20 wt%, the acetonitrile is 200 mL, and the polymerization time is 4.5 h, the hollow PAzo microspheres with about 20 nm shell are successfully fabricated. These hollow PAzo microspheres have excellent reversible photoisomerization, and their first-order rate constant of trans-cis isomerization only decreases 11.8% compared with homopolymer of azobenzene (Homo-PAzo).