Effect of Ultrasonication on Optical Properties and Electronic States of Conjugated Polymer MEH-PPV

Poly[2-methoxy-5-（2＇-ethyl-hexyloxy）-1,4-phenylene vinylene]（MEH-PPV）solutions with different concen-trations were prepared in chloroform for different ultrasonication times.The ultraviolet absorption and photoluminescence（PL）spectra of the MEH-PPV solutions were measured,and the electronic states of the polymer chains under different experimental conditions were studied.The results showed that the effects of ultrasonication on the dilute and concentrated solutions were different.After ultrasonication,the intensity of the absorption peak at 280 nm significantly decreased,relative to the absorption peak at 500 nm for both dilute and concentrated solutions,indicating that the proportion of the two excited states in the polymer chains had changed.For dilute MEH-PPV solutions,the blue-shifted absorption（at about 500 nm）and PL spectra show that ultrasonication also led to polymer chain degradation and thus shortened the effective conjugation length.For concentrated solutions,however,the peak positions of the absorption spectra remained unchanged.In addition,the effects of the solution temperatures on the optical spectra for the MEH-PPV solutions were also discussed.

Preparation of a gene-engineering mutant of bacteriorhodopsin BR-D96V and corresponding poly(vinyl alcohol)-based functional composite films

Bacteriorhodopsin(BR)exhibits,as a membrane protein in Halobacterium salinarum,unique photoresponsive behaviors,and shows promise as a functional information material.A new mutant of BR with the 96th aspartic acid replaced by valine(BR-D96V)was obtained and then a composite film of BR-D96V in a synthetic polymer matrix was prepared in this research.The mutant BR-D96V was expressed in a bacterio-opsin deficient halobacterial strain(L33)by gene engineering.Although valine is very hydrophobic,this point mutant keeps the basic biological activities,namely,photoelectric and photochromic responses.Nevertheless,the lifetime of M intermediate in the BR mutant is nearly two orders of magnitude longer than that of wild-type BR in neutral aqueous solution,which benefits its potential application as an information material.The M lifetime is further significantly prolonged after embedding BR-D96V into poly(vinyl alcohol)(PVA).It was also found that BR-D96V is very sensitive to water content in comparison with wild-type BR and another BR mutant.

Preparation of a cross-linked gelatin/bacteriorhodopsin film and its photochromic properties

Bacteriorhodopsin (BR) is a photochromic membrane protein isolated from a strain of halobacteria.Embedment of BR into a polymeric matrix enables the application of the photoactive protein as an optical material.In this work,a chemically crosslinked BR/gelatin film was prepared.The cross-linked film was found to be highly stable even under extreme alkaline or detergent circumstance while BR maintained its bioactivity.The treatments of base and detergents also led to dramatic prolongation of the lifetime of M photoproduct,which might be beneficial for potential applications such as information storage.The BR/gelatin film was demonstrated to tentatively record a simple pattern.

Applications of self-consistent field theory in polymer systems

The self-consistent field theory (SCFT) based upon coarse-grained model is especially suitable for investigating thermodynamic equilibrium morphology and the phase diagram of inhomo-geneous polymer systems subjected to phase separation. The advantage of this model is that the details of the chain such as the architecture of the chain and the sequence of blocks can be consid-ered. We present here an overview of SCFT approach and its applications in polymeric systems. In particular, we wish to focus on our group’s achievements in applications of SCFT in such fields: simulation of microphase separation morphologies of multiblock copolymers with a complex molecular architecture, interactions between brush-coated sheets in a polymer matrix, mixtures of flexible poly-mers and small molecular liquid crystals at the interface, shapes of polymer-chain-anchored fluid vesicles, self-assembled morphologies of block copolymers in dilute solution, and so on. Finally, the further developments as well as the perspective applications of SCFT are discussed.

Photoinduced Birefringence and Broadband All-Optical Photonic Switch in a Bacteriorhodopsin/Polymer Composite Film

有在 bacteriorhodopsin/polymer 的大光非线性的 Photoinduced birefringence 合成电影被观察。10 -5 相片由抽横梁的 476 nm 导致了的 8.5 ×的一个高折射的索引变化在 6.5 mW/cm 2 的低紧张被到达。基于它，一条宽带所有光的 photonic 开关与一个光控制开关系统被认识到。因为在切换控制横梁的选择，有不同紧张和形状的不同波长的搬运横梁能被调整控制横梁的波长和紧张调制。

Challenging multiphase complex fluids for applications

Modern processing technology is calling the scientific understanding of dynamic processes,where the science of complex fluids plays a central role.We summarize our recent efforts using the generic approaches of multi-scale physics of complex fluids on apparently irrelevant processes,i.e.the mixing of polymer blends,the processing of thermoplastic(TP) toughened thermosetting(TS) composites using phase separation of TP in TS,as well as the enhanced oil recovery using polymer soft gel.It is emphasized that the thorough physical understanding in multi-scales of time and space through the joint efforts of experiment and theory in each scale is the key issue for the modeling of various processes.