Shengang Xu

Polymethylene-b-poly(styrene-co-2,3,4,5,6-pentafluoro styrene) copolymers: synthesis and fabrication of their porous films

New block copolymers of polymethylene-b-poly(styrene-co-2,3,4,5,6-pentafluoro styrene) (PM-b-P(St-co-PFSt)) with controlled molecular weight and narrow molecular weight distribution were synthesized via a combination of polyhomologation of ylides and ATRP copolymerization of styrene and 2,3,4,5,6-pentafluoro styrene. The molecular structure and component of PM-b-P(St-co-PFSt) block copolymers were characterized through 1H NMR, 19F NMR, GPC and elemental analysis. The porous films of these block copolymers were fabricated via the static breath-figure (BF) method. The influence of solvent, molecular weight of copolymer, relative humidity and temperature on the morphology of these block copolymer films was investigated. The porous surfaces of these films presented hydrophobic behaviour with a static water-droplet contact angle of ca. 111°.

A series of dendronized hyperbranched polymers with dendritic chromophore moieties in the periphery: convenient synthesis and large nonlinear optical effects

In this paper, by utilizing low generation nonlinear optical (NLO) dendrimers, in which one sulfonyl-based chromophore was used as an isolation chromophore for two nitro-based chromophores, as the initiator, a new series of dendronized hyperbranched polymers (DHPs), P1–P3, were prepared conveniently through one-pot atom transfer radical polymerization (ATRP) with satisfactory yields. Different from the previous NLO DHPs, of which dendritic NLO chromophores were usually linked into the interior architecture, the NLO chromophores were introduced into the periphery of P1–P3. Thanks to this special structure, all of them demonstrated large NLO effects. For P1, its NLO coefficient d33 value was tested to be 179.6 pm V−1, which, to the best of our knowledge, is among the highest values recorded so far for polymeric materials except for NLO dendrimers. In addition, the optical transparency of P1–P3 could be further improved, due to the utilization of isolation chromophores. Coupled with its high NLO coefficient and convenient synthesis, P1 could serve as a good candidate for real optical application.

Calix[4]resorcinarene-based branched macromolecules for all-optical photorefractive applications

By introducing nonlinear optical (NLO) chromophores to calix[4]resorcinarene, a non-centrosymmetric core, through powerful click chemistry reactions, two branched macromolecules (CRA-CzAZO and CRA-CzCSN) were obtained in satisfactory yields for photorefractive (PR) applications. In comparison with traditional PR materials, which usually need a high external electric field or a poling procedure to realize the PR effect, CRA-CzAZO and CRA-CzCSN can show a good all-optical PR (AOPR) effect, namely showing the PR effect without an external electric field, due to their special non-centrosymmetric topological structure. Two-beam coupling technology is used to prove the PR performance, and a high coupling gain coefficient of 83.2 cm−1 is realized with zero field through optically transparent films of CRA-CzAZO doped with 30% N-ethyl-carbazole as the plasticizer and photoconductor, and 1% C60 as the photosensitizer, indicating that a CRA-CzAZO based composite thin film could serve as a good candidate for real PR applications. More importantly, CRA-CzAZO and CRA-CzCSN provide a new simple design strategy for AOPR materials.

A second-order nonlinear optical dendronized hyperbranched polymer containing isolation chromophores: achieving good optical nonlinearity and stability simultaneously

Large nonlinear optical (NLO) coefficient and good stability, two essential factors to evaluate second-order NLO materials, are difficult to be achieved in one molecule simultaneously. Herein, by utilizing the concept of “isolation chromophore”, “isolation group” and dendritic structure, a dendritic molecule D-NS and a dendronized hyperbranched polymer DHP-NS are prepared to investigate their structure-property relationship. For the small dendritic molecule D-NS, it exhibits a high d33 value of 140 pm/V. But this value can be easily dropped when the temperature is higher than 50 °C, which extremely limits its real application. After introducing D-NS into a dendronized hyperbranched polymer chains, the obtained DHP-NS also shows a high d33 value of 101 pm/V, but much better stability than D-NS. Even when its thin film was heated to 120 °C, no obvious decay can be observed in the d33 value of DHP-NS. This work demonstrates an effective strategy to realize both large NLO effect and good stability simultaneously.

Biomineralized organic–inorganic hybrids aiming for smart drug delivery

Abstract Organic–inorganic hybrid materials have received great interest in the last 10 years in the controlled drug delivery area because of their excellent biocompatible, biomimetic, and pH-sensitive properties. Biomineralization is a biomineral-inspired route to prepare novel organic–inorganic hybrids, which involves a diffusion-controlled deposition of inorganic minerals within porous polymeric matrices. Proper combination of controlled biomineralization technique with the rational choice of polymer templates would lead to the successful development of smart self-assembled drug carriers. The present work mainly summarizes our recent work about the biomineralized organic–inorganic hybrid materials aiming for smart drug delivery including hybrid beads, membranes, and micro/nano gels. Furthermore, prospect for future development of the smart organic–inorganic hybrids is also discussed.