POLY (β-HYDROXYALKANOATES): NATURAL BIOCOMPATIBLE AND BIODEGRADABLE POLYESTERS PRODUCED BY BACTERIA

A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

大肠杆菌poly(A)化mRNA基因片段的RD-PCR克隆

目的研究大肠杆菌(E.coli)中哪些基因mRNA3'端存在poly(A)化。方法利用E.colimRNA中可能存在的poly(A)尾,以oligo(dT)-cellulose进行mRNA的纯化,并以oligo(dT)18为引物逆转录合成cDNA,应用限制性显示-聚合酶链反应(RD-PCR)分离不同组别的基因片段并进行克隆。结果成功克隆100多个基因片段,并对其中30个进行了测序分析。结论细菌mRNA的poly(A)化可能不是偶然和个别的现象。

聚己内酯-碳酸亚乙酯[Poly(CL-EC)]和血管内皮生长因子(VEGF)静电混纺支架的构建及其生物学性能

目的以聚己内酯-碳酸亚乙酯[Poly(CL-EC)]共聚物混合血管内皮生长因子(vascular endothelial growth factor,VEGF),采用静电纺的方法构建纳米支架并检测其生物学性能。方法按照EC/CL共聚物比例为1∶9、1∶6、1∶4,Poly(CL-EC)浓度分别为5%、10%、15%电纺纤维膜,分析电纺纤维膜的表征和力学性能。然后将VEGF按照0ng/g、10ng/g、100ng/g、1μg/g的质量比与Poly(CL-EC)溶液混合,电纺制备纳米支架。对混纺膜进行细胞增殖和黏附试验、乳酸脱氢酶(lactate dehydrogenase,LDH)释放试验、间接溶血试验和皮下植入试验等检测。结果根据Poly(CL-EC)电纺纤维膜的表征和力学性能,我们选用EC/CL比例为1∶6的10%Poly(CL-EC)与VEGF构建混合电纺膜。细胞增殖和黏附试验证实Poly(CL-EC)/VEGF电纺膜具有良好的细胞相容性,尤其是血管内皮细胞;LDH释放试验、接触溶血试验和体内植入试验显示该材料无细胞毒性、有较好的血液相容性和很低的异物反应。结论静电纺构建的Poly(CL-EC)/VEGF具有良好的生物学性能,能够作为组织工程支架材料。

含聚1,3-二氧戊环链段聚合物网络Poly(AA-b-DXL)溶胀度的影响因素研究

继报道了含聚 1,3 二氧戊环 (PDXL)链段具有pH敏感性的可解体聚合物网络Poly(AA b DXL)的制备后 ,对网络的溶胀性能进行了更为详细和深入的研究 .由PDXL与PAA两种亲水性链段组成的网络不仅具有pH敏感性 ,而且可在水中及有机溶剂中溶胀 .研究表明溶剂的溶度参数及网络的结构与组成对网络的溶胀性能有显著的影响 ;

Permeation Characteristics of Light Hydrocarbons Through Poly（amide-6-β-ethylene oxide） Multilayer Composite Membranes

In this paper, poly(amide-6-β-ethylene oxide) (PEBA1657) copolymer was used to prepare multilayer polyetherimide (PEI)/polydimethylsiloxane (PDMS)/PEBA1657/PDMS composite membranes by dip-coating method. Permeation behaviors of ethylene, ethane, propylene, propane, n-butane, methane and nitrogen through the multilayer composite membranes were investigated over a range of operating temperature and pressure. The permeances of light hydrocarbons through PEI/PDMS/PEBA1657/PDMS composite membranes increase with their increasing condensability, and the olefins are more permeable than their corresponding paraffins. For light hydrocarbons, the gas permeances increase significantly as temperature increasing. When the transmembrane pressure difference increases, the gas permeance increases moderately due to plasticization effect, while their apparent activation energies for permeation decrease.

Highly Heat-Resistant Materials for Microelectronics:Hydrodynamic,Optical,and Conformational Properties of Fluorine Containing Poly(Amido-ortho-Hydroxy Amide)

The polycondensation of the mixture of diamines 5,5-methylene bis(2-aminophenol) and 4,4-(hexafluoroisopropylidene)dianiline(molar ratio 0.8:0.2) with isophthaloyl dichloride was used to synthesize poly(amido-o-hydroxy amide)(POA-F)-new heat resistant binder of the composites for microelectronics. The copolymer was fractionated, its hydrodynamic, optical, and conformational properties were researched, and molecular masses(ММ) of the fractions were defined. The polydispersity index was estimated. Based on experimental data, calculation of the size of a segment of Kuhn characterizing degree of an intramolecular orientation order and value of coefficients of the equation of Mark-Kuhn-Hauvink for viscometric and diffusion data were performed. It was demonstrated that introducing 20 mol % of the monomer with-CF3-groups does not lead to any changes in conformational properties of the macromolecules and does not change the degree of intramolecular orientational order(the Kuhn segment length). Optical characteristics of POA-F solutions are virtually similar to the corresponding values for POA prepared with the use of single amine-containing component-5,5-methylene bis(2-aminophenol). The received MM distribution for POA-F(prepolymer) provided the solubility of its films in alkaline solutions. The heat resistance(τ5 and τ10-temperatures corresponding to 5% and of 10% PBO-F mass loss of a polymer) of the powders and the films of PBO, PBO-F were determined. The electrophysical parameters-dielectric permittivity(ε) and dielectric loss tangent(tan δ) of the PBO-F films decreased down to 3.30 and 0.017, in comparison 3.40 and 0.025 for PBO respectively.

SYNTHESIS AND CHARACTERIZATION OF POLY{4-[2-(tert-BUTYLDIMETHYLSILOXY)ETHYL]STYRENE}AND ITS HYDROLYSIS DERIVATIVE

The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.

STRUCTURE AND PROPERTIES OF PHOSPHROUS-CONTAINING POLY(ARYLETHER KETONE)WITH BISPHENOL-A MOIETY

A phosphrous-containing poly（aryl ether ketone） was synthesized derived from bisphenol-A and bis[4-（4- fluorobenzoyl）phenyl] phenyl phosphine oxide （FPPPO） by nucleophilic substitution reaction. The structure of the polymer was characterized by FT-IR, ^1H-NMR and ^31p-NMR. The thermal property of the PAEK was measured by DSC and TGA. The glass transition temperature （Tg） of the polymer was 205℃, and the 5% weight loss temperature under nitrogen was 475℃. Good solubility of the polymer in organic solvents, such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and chloroalkanes was observed, flexible film was obtained from the polymer＇s CH2Cl2 solution. The limiting oxygen index （LOI） of the PAEK was 40, which indicated that organic phosphorus moiety can offer good flame retardant property to the polymer.

Effect of Chemical Doping and Ion Implantation on Cond uctivity of Poly(p-phenylene vinylene) Derivatives

The surface conductivity of poly [ 2-methoxy-5-（3＇-methyl） butoxy]-p-phenylene vinylene （PMOMBOPV） films doped with FeCl3 and H2SO4 by chemical method and implanted by N^＋ ions was studied and the comparison of environmental stability of conductive behavior was also investigated. The energy and dose of N^＋ ions were in the rang 15～35 keV and 3. 8×10^15～9. 6×10^16 ions/cm^2, respectively. The conductivity of PMOMBOPV film was enhanced remarkably with the increases of the energy and dose of N^＋ ions. For example, the conductivity of PMOMBOPV film was 3. 2×10^-2S/cm when ion implantation was performed with an energy of 35 keV at a dose of 9. 6 × 10^14 ions/cm^2 , which was almost seven orders of magnitude higher than that of film unimplanted. The environmental stability of conductive behavior for ionimplanted film was much better than that of chemical doped films. Moreover, the conductive activation energy of ion-implanted films was measured to be about 0.17 eV.

XPS STUDIES ON SURFACE MODIFIED POLY [1-(TRIMETHYLSILYL)-1-PROPYNE] MEMBRANES Ⅱ SURFACE MODIFICATION BY BROMINE VAPOR

Surface modification of poly [1-(trimethylsilyl)-1-propyne] (PTMSP) membranes bybromine vapor has been studied. It is shown that Br/C atomic ratio at the surfaces increased withthe time of bromination until about 60 min, then it reached a plateau. The results of XPS and IRstudies indicated that the addition of bromine to double bonds and the replacement of H on CH_3 bybromine had taken place so that a new peak at 286.0 eV (C--Br)in C_(1s) spectra and some newbands, e. g. at 1220 and 580cm^(-1) in IR spectra were formed. The fact,t Po_2, permeability ofoxygen, decreased and α_(O_2/N_2), separation factor of oxygen relative to nitrogen, increased withbromination time, shows that surface modification of PTMSP by bromine may be an efficient approach to prepare PTMSP membranes used for practical gas separations.

Self-aggregating behavior of poly(4-vinyl pyridine)and the potential in mitigating sand production based onπ-πstacking interaction

Unconsolidated sandstone reservoirs are most susceptible to sand production that leads to a dramatic oil production decline.In this study,the poly(4-vinyl pyridine)(P_(4)VP)incorporated with self-aggregating behavior was proposed for sand migration control.The P_(4)VP could aggregate sand grains spontaneously throughπ-πstacking interactions to withstand the drag forces sufficiently.The influential factors on the self-aggregating behavior of the P_(4)VP were evaluated by adhesion force test.The adsorption as well as desorption behavior of P_(4)VP on sand grains was characterized by scanning electron microscopy and adhesion force test at different pH conditions.The result indicated that the pH altered the forms of surface silanol groups on sand grains,which in turn affected the adsorption process of P_(4)VP.The spontaneous dimerization of P_(4)VP molecules resulting from theπ-πstacking interaction was demonstrated by reduced density gradient analysis,which contributed to the self-aggregating behavior and the thermally reversible characteristic of the P_(4)VP.Dynamic sand stabilization test revealed that the P_(4)VP showed wide pH and temperature ranges of application.The production of sands can be mitigated effectively at 20-130℃ within the pH range of 4-8.

STUDIES ON THE REGULAR COPOLYMERS OF POLY (1, 4-PHENYLENETEREPHTHALAMIDE)

Two types of the regular copolymer of poly (1, 4-phenyleneterephthalamide) were synthesized by the low temperature solution polycondensation in NMP-CaCl_2 solvent system, using the piperazine or 2,5-dimethylpiperazine as the third components introduced in the main chain of poly (1, 4-phenyleneterephthalamide). The properties of copolymers were characterized by IR, SEM, X-RAY diffraction, polarizing microscopy, TGA and solubilities.Experimental results showed that the copolymers had good solubility and thermal stability, the concentrated sulfuric acid (～98% ) solution of regular PPTA copolymers had liquid crystalline proper-

Preparation of High Molecular Weight Poly(L-lactide-co-caprolactone)(85-15)

Poly（L-lactide-co-caprolactone）（85-15）[P（LLA-CL）（85-15）] was synthesized from high purity L-lactide and e-caprolactone using tin octoate as initiator by ring-opening polymerization, and characterized by infrared spectrum and IH-NMR spectrum. The synthesized P（LLA-CL）（85-15） is a random copolymer. The influences of polymerization temperature, polymerization time, dosage of initiator and polymerization pressure on the weight average molecular weight and the polydispersity index of P（LLA-CL）（85-15） were investigated. The optimum preparation conditions of P（LLA-CL）（85-15） are： the polymerization pressure is less than 0.5 Pa, the polymerization temperature is 130 ~C, the n（M）/n（I） ratio is 8 000/1, and the polymerization time is 36 h. Under the condition, the weight-average molecular weight of prepared P（LLA-CL）（85-15） is 65.6x 104, and molecular weight distribution coefficient is 1.15.

Rapid Expansion of Supercritical Solution of Poly (1,1,2,2- Tetrahy-droperfluorodecyl Acrylate)

Poly(1,1,2,2- tetrahydroperfluorodecyl acrylate) (poly (TA-N)) was synthesized in laboratory. The resulting morphology of rapid expansion of supercritical solution (RESS) sprays of poly(TA - N) was investigated. At apre - expansion temperature of 45℃), amorphous polymer was formed. At temperature around 60 ℃ to 80 ℃ , fibers were formed. Increase of temperature increasesparticle size slightly. At temperature of 105℃ , most of particles are spheres. The RESS is an attractive process. To apply the polymers desired for coating applications in an organic solvent - free process that is economically viable , and it will have implications for pollution prevention during polymer film

Poly{[4-(hydroxyl)(tosyloxyl)iodo]styrene} Promoted Halotosyloxylation Reaction of Alkynes

Halotosyloxylation reaction of alkynes with iodine or NBS or NCS was efficiently promoted by the poly{[4-(hydroxyl)(tosoyloxyl)iodo]styrene}.

IONIC CONDUCTIVITY OF POLY (β-ALKOXYCARBONYLETHYLMETHYLSILOXANE)-LiClO_4 CROSSLINKED FILMS

Poly (β-carboxyethylmethylsiloxane)-LiClO_4 and poly (β-alkoxylethylmethylsiloxane)-LiClO_4 crosslinked fllms have been prepared. The ionic conductivity of the films depends on the polymer species, concentration of lithium perchlorate, temperature and content of crosslinking agent. The effect of high polar organic solvent 1, 4-butyrolactone on the ionic conductivity and mechanical properties of poly (β-carhoxyethylmethylsiloxane )-LiClO_4 system was also investignied.

Big Third-order Nonlinear Optical Properties of Two Poly[(3-alkylthiophene-2, 5-diyl)-(benzylidenequinomethane-2, 5-diyl)] Derivatives

Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octylthiophene2,5-diyl) -(p-N, N-dimethylamino ) benzylidenequinomethane-2, 5-diyl)] (POTDMABQ), were synthesized.The band gaps of the two polymers are calculated as 1. 75 eV for PBTDMABQ and 1. 69 eV for POTDMABQ,respectively. The homogenous films of the two polymers were prepared and their third-ordernonlinear optical properties were studied by the backward degenerate four-wave mixing at 532 nm. Byusing the relative measurement technique, the third-order nonlinear optical susceptibilities ofPBTDMABQ and POTDMABQ are calculated as 5. 62 X 10^(-9) and 1. 22 X 10^(-8) ESU, respectively. It isfound that substituted alky groups have strong effects on the band gap and nonlinear opticalproperties of the two polymers. The relatively big third-order nonlinear optical susceptibilitiesand small band gap of POTDMABQ resulted mainly from the longer alkyl with strong electron-donatingability can enhance the delocation degree of conjugated π electronics.