ELECTRONIC EFFECTS OF POLYFLUORINATED SUBSTITUENTS ON THE POLYMERIZATION AND THE PROPERTIES OF POLYTHIOPHENES

Three series of polythiophenes containing fluoroalkoxy and fluoroether substituentswere prepared by electrochemical polymerization. The effect of substituents with fluoro-alkoxy or ether functional groups on the electrochemical polymerization of thiophene mono-mers and properties of the obtained polymers were analyzed. The introduction of a flu-oroether functional group at the 3-position of the thiophene ring leads to an increase ofthe oxidation potential of the monomer and to a decrease of the conductivity of the re-sulting polymers, even with the use of a CH_2 group as spacer. Conversely, the presenceof an oxygen atom directly at the 3-position of the thiophene ring, which offsets the nega-tive withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conductingpolythiophenes.     

STRUCTURAL ANALYSIS OF PEKEKK（T／I） USING WAXD, IMAGING PLATES AND SAXS

Structures and crystal form transition of the novel aryl ether ketone polymer containing meta-phenylene linkage: PEKEKK(T/I) were investigated by wide angle X-ray diffraction (WAXD), imaging plates (IPs) and small angle X-ray scattering (SAXS). The energy of activation of the decomposition reaction and degree of crystallinity of PEKEKK(T/I) were determined by WAXD and thermo-gravimetric analysis (TGA), respectively. Results obtained fi‘om WAXD and IPs show that crystal forms I and II coexist in the PEKEKK(T/I) samples isothermally cold crystallized in the temperature range from 180℃ to 240℃ and only form I occurs in PEKEKK(T/I) samples isothermally cold crystallized at 270℃. The radius of gyration (Rg), thickness of microregions with electron-density fluctuations (E) and distribution of particle sizes were investigated by SAXS.     

桥基取代的四氮杂大环配合物热力学稳定性的研究

用电位pH法测得了5,5,7,12,12,14-六甲基-1,4,8,11-四氮杂环十四烷与Co~(2+),Ni~(2+),Cu~(2+),Zn~(2+)生成配合物的稳定常数。探讨了它们在水溶液中的可能结构,并对大环碳上甲基取代的取代数与稳定常数间的关系作了研究.发现它们在水溶液中结构为五配位的四方锥体。大环碳原子上的氢被烷基取代后,配合物稳定性下降,下降的主要原因是空间效应并非电子效应之故.     

MISCIBILITY, THERMAL STABILITY AND RETENTION OF PVP FOR CROSSLINKED PVA/PVP BLENDS

The thermal behavior, miscibility, crystallite conformation and thermal stability ofcrosslinked(CL-) PVA/PVP blends were studied by DSC and TG methods, respectively. DSCresults showed that in the blend, the crystallinity,T_m and T_c of PVA were obviously lower thanthose of pure PVA; the crystal growth changed from three dimensional to two dimensional andonly a single T_g was detected. These facts demonstrated that this crystalline and amorphousblend have good miscibility. TG curves showed that providing the quantity of K_2S_2O_8 added ismore than 3 wt%,in the blends PVA will form a stable CL-network, whose thermal degradationtemperature was near to that of PVP. But crosslinking reaction will not take place for PVP. Theprocesses of thermal degradation of CL-blends are based on combining both the thermaldegradation of PVP and that of PVA crosslinked with corresponding quantity of K_2S_2O_8 CL-agent, respectively. The UV measurements showed that 75 wt% of PVP may be remained in CL-blend hydrogelscrosslinked by adding (3--5 wt% )K_2S_2O_8. This is mainly due to the stable CL-network formed and the good compatibility and properentanglement between the composites in the CL-blends.     

STRUCTURAL CHARACTERIZATION OF POLYETHYLENES BY DSC ANALYSIS AFTER CRYSTALLIZATION SEGREGATION*

The molecular structure of polyethylene (PE) samples with various comonomers including propylene, 1-buteneand 1-hexene was investigated by DSC and ~(13)C-NMR techniques. The density of the samples varies from 0.948 g/cm~3 to0.917 g/cm~3, and the molecular weight determined by the GPC method is in the range of 1～2×10~5. The branch point contentof the samples was determined by ~(13)C-NMR measurements and was found to be less than 20 per 1000 C atoms along themain chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or thesegment length distribution of PEs. The crystallization segregation was performed in a successive annealing process atdecreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of eachannealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs,more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves wereusually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters,the average melting point, T_(mAV), and the root-mean-square deviation of melting temperature, (ΔT_(mAV)~2)~(1/2), were proposed.T_(mAV) is corresponding to the average segment length due to branching and (ΔT_(mAV)~2)~(1/2) gives information about the width ofthe segment length distribution. Experimental results show that both the degree of average melting temperature depressionand the width of the distribution seem to increase with increasing the branching content and are dependent on the type ofcomonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It wasconcluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.     

ENVIRONMENTAL STABILITY OF THE POLYENE PREPARED BY DEHYDROCHLORINATION OF POLY(VINYL CHLORIDE)

A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity ofpolyene sequences according to its FT-infrared and Raman spectra. The environmental stability of the polyene was alsostudied by IR, Raman spectra and elemental analysis. Experimental results demonstrated that the polyene was susceptible toair and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups. The polyenesequences were shortened and its dispersity became broader due to the effect of dioxygen.     

THERMAL ANALYSIS OF ACRYLIC FIBERS

This is a comprehensive survey of our work during the past thirteen years on the thermal analysis of acrylic fiber, including some recent, unpublished results.     

KINETIC ANALYSIS OF CO-CONDENSATION POLYMERIZATION OF AB2 AND AB MONOMERS

This work deals with the kinetics of co-condensation polymerization of AB2 and AB monomers, giving expressions of the two-dimensional molecular weight distribution function and the number/weight average molecular weights of the resulting copolymers. The two-dimensional molecular weight distribution depends on two indices, n and l, which are the respective numbers of AB2 and AB units in a copolymer species. The evolution of the two-dimensional weight and z distributions during the co-condensation polymerization has been evaluated systematically. Finally, the two-dimensional distribution was transformed into a one-dimensional molecular weight distribution with only one variable (the molecular weight of the products instead of the degree of polymerization). The calculated results show that the highly branched copolymer has a very broad molecular weight distribution when the co-condensation polymerization approaches completion.     

THERMAL ANALYSIS OF POLYPROPYLENE-b-POLYETHYLENE DIBLOCK COPOLYMERS AND CORRESPONDING BLENDS

Difference in thermal behavior of presumed polypropylene-b-polyethylene block copolymers(PP-PE) and corresponding PP+PE blends was studied. Different views in the literature were unified in our observation that faster cooling rate yielded only one exothermal peak for the blends, while slower cooling rates revealed both PP and PE exothermal peaks. Further details on when a single or double exothermal peaks would appear are discussed. Melting and crystallization temperatures for both PP and PE in blends were found to be a few degrees higher than for PP and PE in block copolymers. Thus, thermal analysis can be used to identify PP-PE block copolymers. These phenomena and the lower △H_f-values of PP and PE in block copolymers than the △H_f-values of pure homo-PP and -PE (for PE even more so) are explained in terms of restricted block movement due to covalent bond between blocks and of crystallization processes in block copolymers. The presence of block structure in the PP-PE samples studied is inferred.     

THERMAL ACTIVATION OF IMMOBILIZED PAPAIN

Papain (Papainase, EC 3.4.22.2) was immobilized on porous silica beadsby cross linking with glutaraldehyde. The thermal activation of this immobilized papainin aqueous system was found at a temperature range from 50 to 90℃. The higher thetemperature, the more active the immobilized papain will possess. At the same time,the durability of the immobilized papain on heating was greatly improved. The effect ofadditives and salts on the activity of the immobilized papain were also studied. The resultsshowed that the additives and some of the salts studied could markedly enhance the activityof the immobilized papain at elevated temperature.     

THEORETICAL ANALYSIS OF KINETICS OF NONISOTHERMAL CRYSTALLIZATION OF POLYMERS

The classical crystallization theories proposed by Avrami, Evans, and Mandelkern wereextended to the nonisothermal situation. The expressions derived from the classical equations canbe expressed in either the differential form or the integral form. A method was provided so as toobtain the parameters characterizing the crystallization rate and mechanism from DSC curves withseveral constant heating or cooling rates. The rate constants of crystallization obtained from bothisothermal and nonisothermal curves of poly(ethylene terephthalate)were compared.     

THE EFFECT OF PHOTO-CROSSLINKING ON THE ORIENTATION STABILITY OF POLYVINYL ALCOHOL CONTAINING 4-NITRO-4′-ALKOXYSTILBENE AND CINNAMYL PENDENT GROUPS*

Crosslinking is one of the effective routes for improving the orientation stability of poledpolymer films. The derivative of polyvinyl alcohol containing 4-nitro-4'-alkoxystilbene andphoto-crosslinkable cinnamyl groups as side chains has been synthesized. The in-situ simul-taneous photo-crosslinking poling of synthesized polymer films has been performed. Thesecond order nonlinear optical coefficient d_(33) of poled film is 11 pm/V. The SHG mea-surements show that the break-over temperature of SHG signal is raised obviously afterirradiation, its orientation stability is doubled as compared with that of non-crosslinkingsamples.     

SYNTHESIS AND CHARACERIZATION OF LADDER-LIKE POLYDECYLSILSESQUIOXANE*

Ladder-like polydecylsilsesquioxane (LPDS) was synthesized by a preamminolysis reaction ofdecyltrichlorosilane with ethylene diamine, followed by hydrolysis and polycondensation reaction. LPDS issoluble in a nonpolar solvent such as heptane and insoluble in a high polar solvent such as methanol. It wascharaterized by IR, ~1H-NMR, ~(29)Si-NMR, GPC and X-ray diffraction.     

SYNTHESIS AND CHARACTERIZATION OF COMB-SHAPED POLYBUTADIENES

Polybutadiene (PB) was chlorinated with t-BuOCl without chain crosslinking and degradation togive chlorinated polybutadiene (Cl--PB) with active allylic chlorine atoms on the backbone. Comb-shaped PB was prepared by coupling of Cl--PB with "living" PB anions in a mixed solvent of cyc-lohexane and tetrahydrofuran. Characterization by GPC and osmometry showed that purifiedproducts were welldefined comb-shaped PB composed of low polydispersity backbone chain andrandomly distributed grafts of uniform length. The averagr number of branches could be variedin a wide range to meet the needs of structure-properties relationship studies.     

POLYMERIZATION OF A NEW SUBSTITUTED ACETYLENE BEARING A FURAN RING WITH PALLADIUM ACETYLIDE CATALYSTS

A substituted polyacetylene bearing a furan ring, poly(2-propynyl 2-furoate) (PPF), was synthesized for the first time with palladium acetylide complex catalysts in CHCl3 at 60℃ to give a soluble and stable polymer with a yield of ca.75%. Some features for polymerization of 2-propynyl 2-furoate are described and discussed. The resulting polymer was characterized by IR, GPC and ^1H-NMR analysis.     

A DYNAMIC MECHANICAL ANALYSIS STUDY OF THE TRANSITION BEHAVIOUR OF I-PP/EPDM BLENDS

The transition behaviour of the blends of isotactic polypropylene (i-PP) with ethylene-propylene terpolymer (EPDM) containing 42 wt% propylene was investigated by dynamic mechanical analysis technique (DMA). Owing to its high propylene content, EPDM is compatible with i-PP to some degree. The interaction between the two components was strengthened. As expected, for partially compatible system the glass transition temperature of i-PP in the blends shifted to lower temperature. It was found that there existed two transitions, αEPDM and βEPDM, for the EPDM used in this work. The former was considered to be the glass transition of the random chain segments of EPDM, while the latter the local motion of the long ethylene sequences in EPDM. The unusual transition behaviour of αEPDM in the blends was explained in terms of the greater thermal expansion of EPDM and the compatibility of the two components. On the other hand, the βEPDM changed with the composition of the blends in a regular manner.     

SYNTHESES AND ADSORPTION PROPERTIES OF PHENOL-FORMALDEHYDE-TYPE CHELATING RESINS BEARING THE FUNCTIONAL GROUP OF TARTARIC ACID

Several kinds of novel chelating resins bearing the functional group of tartaric acid (TTA-FQ-12, TTA-FQ-23, and TTA-FQ-34) were synthesized by reacting epoxy maleic anhydride, which was prepared through the oxidization reaction of maleic anhydride by hydrogen peroxide, with phenol-formaldehyde resin containing polyamine (FQ resins series). The effects of such factors as reaction time, reaction temperature and pH value on the loading capacity of TTA in resins were investigated. The results showed that the optimum reaction conditions are as follows: time 9-12h; temperature 90-105℃;pH value 6-10. The loading capacities of TTA can reach 0.15, 0.14, and 0.11 mmol/g^-1 when the functional group of FQ resin was -OCH2CH2NHC2H4NH2, -O(CH2CH2NH)2C2H4NH2 and -O(CH2CH2NH)3C2H4NH2), respectively. The structures of resins were characterized by FTIR spectra. The primary study on the adsorption properties of the resins for metal ions showed that there are two kinds of adsorption mechanisms i.e. ion exchange and chelate in the adsorption process. TTA-FQ resins have much higher adsorption selectivity for Pb^2 and Zn^2 than for Cu^2 and Ni^2 . These resins can probably be used for separating Pb^2 or Zn^2 in the mixture of metal ions or for treating wastewater containing heavy metal ions.     

STUDY ON THE POLYMERIZATION KINETICS AND STABILITY OF P(UA)/MMA MICROEMULSION*

 Urethane acrylate anionomer (APUA) as a kind of new type polymerizable emulsifier was synthesized using 2,4-toluene diisocyanate (TDI), polypropylene glycol (PPG), 2-hydroxyethyl methacrylate (HEMA) and dimethylolpropionic acid (DMPA). The critical micelle concentration (CMC) of APUA was measured by the methods of conductance and surface tension. The comparative studies between polymerizable emulsifier AUPA and conventional emulsifier sodium dodecyl sulfate (SDS) were carried out in the emulsion polymerization of methyl methacrylate (MMA). Polymerization kinetics,stability, size and morphology of the latex particles were investigated. It was found that in APUA both water soluble initiator potassium persulfate (KPS) and oil soluble initiator 2,2'-azobisisobutyronitrile (AIBN) can start the reaction of MMA, and the polymerization rate and yield were very high. On using AIBN as an initiator, the conversion-time behavior of MMA with APUA as emulsifier was different to that of SDS as emulsifier, signifying a different nucleation mechanism of the polymer latex particle. The average size of the two kinds of particles is about 50 nm. The particle size decreases with increasing emulsifier concentration. On using KPS as the initiator, APUA as emulsifier, cross-linking hydrogel of PMMA would be formed, but SDS was used as emulsifier and the hydrogel of PMMA was not present.     

ASPHERICITY AND PROLATENESS OF LINEAR AND CIRCULAR MACROMOLECULES

The shape asymmetry of gaussian models of linear and circular macromolecules hasbeen numerically invesigated in terms of asphericity and prolateness parameters. Theseparameters are found to decrease with increasing length for the macromolecule eitherconfined to a plane or in three dimensions. The effect of dimensionality on theseparameters is visible only for low dimensions and is generally weak. As dimensionality goesto infinity, it is found that asphericity and prolateness for both chains and rings approachslowly yet descendingly values of corresponding asphericity and prolateness factors, withthe exception of the chain which shows a minimum value of asphericity when theembedding space has a dimensionality of four.