COMPATIBILITY AND PHASE BEHAVIOR OF PS/SBR BLEND Ⅰ. EFFECT OF MOLECULAR WEIGHT OF PS

The results of this study reveals not only the sensitivity of the compatibility of PS with SBR to the molecular weight (MW) of PS and temperature, but also some other interesting characteristics, i. e., unusual morphology change during the process of mixing with increase in temperature of specimen preparation observed under optical microscope and double-peak UCST curves for three blends with PS of low MW from DSC data. Acording to the amount of inward shift of the component T_g's and the broadening of the transition regions, it may be said that this polymer pair is compatible only when the MW of PS is low, and even then there still exists micro-heterogeneity.     

CROSSLINKING AND COMPATIBILIZATION IN BLENDS OF POLYSTYRENE AND POLYETHYLENE

This paper investigated the influences of butadiene rubber (BR) and dicumylperoxide (DCP) on thermal and rheological behaviour, morphology and mechanical proper-ties of PS/LLDPE/SBS blend. Addition of DCP alone was found to decrease the mechanicalproperties of PS/LLDPE/SBS blend due to the decomposition of PS. When BR was addedtogether with DCP, it is found that the co-crosslinking of BR, SBS and PE takes place,and the decomposition of PS is reduced simultaneously because of the consumption of thefree radicals in the crosslinking process. Synergism was thus realised which resulted in theimprovement of the ductility of blend.     

MICROENVIRONMENTAL EFFECTS OF THE HELICAL CONFORMATIONS OF AMYLOSE AND ITS DERIVATIVES——CATALYTIC EFFECTS OF SODIUM CARBOXYMETHYLAMYLOSE ON THE HYDROLYSIS OF VARIOUS ESTERS OF N-ALKYL-3-HYDROXYPYRIDINIUM IODIDE

Hydrolysis of various carboxylic esters of N-alkyl-3-hydroxypyridinium iodide(2—5) has been studied, both in the absence and in the presence of sodium carboxymethylamylose(NaCMA 1). In the absence of Na-CMA, the hydrolysis of all four substrates follows 2nd-order kinetics when HPO_4~- and CH_3CO_2~- ions are used as the attacking nucleophites. In the presence of 1, however, the course of the reaction depends on the structure of the substrates. For 2 and 3, the observed rate constants k_(obs) are independent of the eoncentration of 1 added, but for those with long hydrocarbon chains, i. e. 4 and 5, the hydrolysis follows MichaelisMenten kinetics. All other experimental results also indicate the formation of supramolecular(incluston) complexes between the Na-CMA host molecules in helical conformations and theesters 4 and 5. In comparison with the bimolecular processes in the bulk phase, the catalytic efficiencies(k_c/K_d) of these supramolecular systems are 3.7×10~4 and 1.7×10~4 times that of the aceta     

EFFECT OF PLASTICIZER ON THE MICROSTRUCTURE OF PS/PVC BLENDS

In this work, controlling of the particle size of PVC in PS/PVC blends was studied. Itis shown that viscosity ratio and particle size can be changed by adding a third composition,such as plasticizers, and the distribution of the third composition in two phases plays avery important role in controlling viscosity ratio and particle size. When DOP was used asthe plasticizer of PVC in PS/PVC blends, the particle size of PVC could not be reduceddue to the transference of DOP into PS phase. When polycaprolactone (PCL) was usedas the plasticizer of PVC in the same blends, the particle size of PVC could be descreasedobviously because PCL does not migrate to PS phase.     

CHEMISTRY OF THE PERFLUORO AND POLYFLUORO ORGANIC COMPOUNDS——THE RELATIVE EASE OF FORMATION OF TWO PERFLUOROALKYL R ADICALS

The relative rates of formation of perfluoro iso-propyl radicals (i—C_3F_7,5(i)) and perfluoro n-propyl radicals (n—G_3F_7, 5(n)) are reported. The relative rate constants of β-scission and of bromine abstraction by perfluoro-(α-alkoxyethyl)radicals(RFOCFCF_3:R_F=i—C_3F_7, 3(i); R_F=C_3F_, 3(n)), designated as kr(i) and k,(n), were measured at 7 temperatures in the range of 50—80℃, thence the ratio of the relative rate constants of formation of perfluoro iso-propyl radicals (5(i) and perfluoro n-propyl radicals (5(n)), K_β(i):K_β(n), were obtained. These ratios range from 540—680 at 50℃ to 400—590 at 80℃, much larger than those of the corresponding hydrocarbon radicals. Finally, the differences of activation-free-energy differences between 3(i) and 3 (n), △G~≠(i—n), together with the corresponding enthalpy and entropy terms, △H~≠(i—n), △S~≠(i- n), were calculated. These kinetic parameters indicate that the much higher rate of formation of the perfluoro iso-propyl radicals is caused     

SYNTHESIS AND PROPERTIES OF POLYSTYRENE／LAPONITE NANOCOMPOSITES

Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS.     

SELF-ASSEMBLY OF ROD-COIL DIBLOCK COPOLYMERS——INFLUENCE OF THE ROD LENGTH

The self-assembly of five narrowly distributed novel rod-coil diblock copolymers, poly(styrene-block-(2, 5-bis[4-methoxy-phenyl]oxycarbonyl) styrene) (PS-b-PMPCS), in p-xylene, a selective solvent at room temperature, was studied. Therod-coil copolymers, which have the same PS length but different PMPCS length, were synthesized by 2,2,6,6-tetramethyl-I-piperidinyloxy (TEMPO) mediated living free radical polymerization. The influence of the rod length on the self-assemblymorphology was studied by transmission electron microscopy (TEM). At a concentration of 2.0 mg/mL, those copolymerswith relatively shorter PMPCS length (copolymers 1 and 2) form individual spherical micelles; those with relatively longerPMPCS length (copolymer 3 and 4) form "pearl chains" coexisting with individual spherical micelles; the ones with longestPMPCS length form "pearl chains" coexisting with occasionally formed nanofibers. The diameter of all the morphologieswas controlled by the rod length. This gives us a way to govern the self-assembly morphology by altering the length of oneblock in the block copolymer.     

THE PREPARATION AND CHARACTERIZATION OF SBR／PS CORE-SHELL PARTICLES BY GAMMA IRRADIATION

A kind of core(SBR)-shell(PS) particles was synthesized by using SBR latex and grafting with St under gamma irradiation. The influences of absorbed dose and dose rate on the grafting yield of PS on SBR seed latex have been investigated. Results show there was a transition layer which contained the SBR/PS graft copolymer between the SBR core and PS shell. Dynamic laser scattering (DLS) and differential scanning calorimetry (DSC) results confirm the existence of grafted polystyrene, and transmission electron microscope (TEM) observation verifies the core-shell structure of SBR-g-PS latex. Such SBR/PS core-shell latex could be processed easily to ultrafine rubber powders by using spray drying and expected to be used as an impact modifier for PS.     

LINEAR ENTHALPY RELATIONSHIPS BETWEEN HEATS OF FORMATION OF COMPLEX COMPOUNDS AND HEATS OF PRO TONATION OF LIGANDS——COPPER(Ⅱ)-N-(PARA-SUBSTITUTED PHENYL) GLYCINES

The heats of protonation of N-(para-substituted phenyl) glycines (R—C_6H_4—NHCH_2COOH, R=CH_3O, CH_3, H, C1) and the heats of formation of these amino acids with copper(Ⅱ) have been determined calorimetrically at 25℃ in 30% (v/v) ethanol in the presence of 0.1M sodium perchlorate. The data obtained conform nicely to the equation △H_(ML)-Q-β△H_(HL) where △H_(ML) denotes the heats of formation of complex compounds, △H_(HL) denotes the heats of protonation of the ligands, and Q and β are constants.     

STUDY AND APPLICATION OF SPECTROPHOTOMETRIC DETERMINATION OF MICRO AMOUNTS OF BISMUTH WITH MESO—TETRAKIS—(4—N—TRIMETHYL AMMONIUMPHENYL)PORPHINE

A new highly sensitive spectrophotometric method has been developed for the determination of micro amounts of bismuth (Ⅲ), based on the formation of Bi (Ⅲ)—meso—tetrakis—(4—N—trimethylammonium phenyl) porphine [T (4TMAP) P] complex. In the presence of Cd (Ⅱ), Bi(Ⅲ) reacts almost instantaneously with T (4TMAP)P in a 0. 6 mol/l NaAc—HAC buffer (PH5.8) at room temperature. The composition of the complex is T(4TMAP)P: Bi=1:1. The absorbance complex obeys Beer's law over the Bi(Ⅲ) concentration range 0.1—1.4 μg/ml. The linear relative coefficient γ is 0.9998. The apparent molar absorptivity was 1.75×10~5 1. mol~(-1). cm~(-1) at 463nm. The relative standard deviation of the method is 1.50％ for Bi(Ⅲ) 7ug/10ml (10 determinations). The interference of foreign ions has been examined. This simple and rapid method can be applied to the assay of Bi(Ⅲ) in some tablets directly.     

A COMPARATIVE STUDY OF CHAIN DYNAMICS OF DI-AND TRI-BLOCK COPOLYMERS IN SEMIDILUTE SOLUTION IN A NON-SELECTIVE SOLVENT

The chain dynamics of a pair of diblock poly(styrene-b-butadiene) (PS210-b-PB960) and triblock poly(styrene-b-butadiene-b-styrene) (PS200-b-PB1815-b-PS200) copolymers in both dilute and semidilute toluene solutions has been comparatively studied by dynamic laser light scattering. As expected, the mutual diffusion of individual chain changes into a fast cooperative diffusion of the chain segments (“blobs“) between two neighboring entanglement points for both the copolymers as the solution changes from dilute to semidilute. Further increases of the concentration lead to a second slow relaxation mode. For the triblock chains, there exists an additional middle relaxation between the fast and the slow modes.with 0.33 ＜α＜ 0.44, much smaller than 0.75 predicted or 0.72 observed for linear homopolymer chains in good solvent. It implies that the solvent quality of toluene for PB might not be as good as that for PS. Due to such a difference in solubility, it is reasonable to speculate that the PB and PS blocks are transiently segregated in semidilute solution. The relaxation of these transient PB and PS richer domains leads to the observed slow relaxation. Such a speculation is supported by the appearance of an additional slow relaxation mode in the study of polyisoprene-b-polystyrene-b-polyisoprene in semidilute solution in cyclohexane, a non-selective solvent, in which we alternated the solubility difference by a variation of the solution temperature.     

NETWORK ENCAPSULATION OF NANOMETER CaCO_3

The encapsulation of stearic acid coated nanometer CaCO3 by a polystyrene (PS) network via emulsion polymerization is described, where γ-methacryloxypropyltrimethoxysilane (MPS) was used as an efficient crosslinker. The important factors such as the type and amount of surfactant and initiator and the content of CaCO3 are investigated as well as the role of MPS. It has been shown that little PS was extractable with only 0.6 wt% of MPS (relative to styrene). The cationic surfactant cetyl trimethylammonium bromide (CTAB) proved more effective than the anionic surfactant sodium dodecyl sulfonate (SDS). The yield rises, particles become smaller and size distribution broadens with increased amount of CTAB. It is also found that either 2,2′-azobis(isobutyronitrile) (AIBN) or ammonium persulfate (APS) is suitable for attaining high monomer conversion. With increased amount of CaCO3, the encapsulation ratio can be varied from 17.9 to 3.6, while monomer conversion and yield decrease slightly. FT-IR spectra of the products after extraction indicate tight encapsulation between PS and CaCO3, and TEM photographs of composite particles with well-defined core-shell structure give direct evidence of encapsulation.     

A COMPARISON OF THE DETERMINATION OF STABILITY CONSTANTS OF COMPLEXES OF Cd(Ⅱ)WITH AMINO ACIDS AND SIMPLE PEPTIDES USING MICRO—pH—METRIC TITRATIONS AND CYCLIC VOLTAMMETRY

This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly,Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra-tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol·dm~(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com-puter program and cyclic voltammograms were collected,stored and manipulated using the EG and GCONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible usingvoltammetry.Evaluation of results from the two techniques suggests that stability constants for thespecies[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are morereliable when determined by pH-metric titration.     

ESR STUDIES OF SPIN-TRAPPED RADICALS IN GAMMA-IRRADIATED POLYCRYSTALLINE PYRIMIDINE NUCLEOSIDES——CYTIDINE, DEOXYCYTIDINE, URIDINE AND DEOXYURIDINE

Room-temperature free radicals produced in four gamma-irradiated polycrystalline pyrimidine nucleosides (cytidine, deoxycytidine, uridine and deoxyuridine) were studied by an improved spin trapping and ESR methods with NtB (nitroso-t-butane) serving as the spin trap. The presence of three types of radicals was ascertained in all samples, i.e. —C(5)H—C(6) H_2—and —C(5)H_2—C(6)H— base radicals, and —C(5')H_2— ribose radical evolving from HOC(5')H—C(4')H<. In addition, radicals in which the unpaired electron was located on ribose C(1') and C(4') sites were tentatively distinguished. Stress was laid on the discussion of the mechanism of formation of ribose radicals.     

KINETICS OF CARBON DIOXIDE——PROPYLENE OXIDE COPOLYMERIZATION

Kinetics of the anionic coordination copolymerization of carbondioxide (M_1)and propylene oxide(M_2) was studied for the first time on thebasis of the liquid vapor equilibrium.The reactivity ratio r_2 was determined tobe 0.2 by a modified integral method,while r_1 was recognized to be zero.These values indicate that the reaction in the presence of excess carbon dioxidetends to form alternating eopolymers.The rate of polymerization was found toobey the following equation:R_p=(?)M_2~2/M_1where M_1 and M_2 (mol/L) are concentrations of the monomers.and C(g/L) isamount of the catalyst.For the polymerization,a mechanism is proposedinvolving initiation by forming M_2-catalyst complex,propagation by repeatedM_1 and M_2 insertion at the active center,and a shielding of the active centerC by M_1.This mechanism predicts the dependence of R_p on the concentrationsas observed.     

EFFECTS OF STYRENE-ETHYLENE/PROPYLENE DIBLOCK COPOLYMER (SEP) ON THE COMPATIBILIZATION OF PP/PS BLENDS

The effects of styrene-ethylene/propylene (SEP) diblock copolymer on the morphology and mechanical propertiesof polypropylene/polystyrene (PP/PS) blends were investigated. The results showed that SEP diblock copolymer, acting as acompatibilizer in PP/PS immiscible blends, can diminish the coalescence of the dispersed particles, reduce their averageparticle size, change their phase morphologies significantly, and increase the mechanical properties. It was found that SEP has better compatibilization effects on the PP/PS (20/80) blends.     

Structure and Photosynthetic Mimicking of Bis（2,6—bis（benzimidazol—2—yl）pyridine）manganese（Ⅱ）

Mn(bzimpy)2(1)[bzimpy=2,6-bis(benzimidazol-2-yl)pyridine],a mononuclear manganese(Ⅱ）complex,was synthesized by the reaction of Mn(OOCMe)2 with bzimpy in absolute ethanol.The complex was structurally characterized by elemental analysis,cyclic voltammetry,and X-ray crystallography.In the complex,the manganese-nitrogen distances were different,and the geometry and the metal ion environment showed the distortion.The cyclic voltammetric measurements have been performed to assess its redox characteristics.The presence of oxidation wave at 0.62V and 0.081V vs.SCE or 0.8V and 1.0v vs.NHE suggested that this complex could catalyze the oxidation of water,therefore,simulate the water-oxidizing complex(WOC) of photosystem Ⅱ (PS Ⅱ).The measurements of photoreduction of 2,6-dichlorophenolindophenol (DCPIP),and oxygen evolution in the manganess-depleted and the comples 1-reconstituted PS Ⅱ preparations just support our conjecture.     

PHENOMENON OF LEFT-RIGHT SHIFTS OF S-SHAPED CURVE——THE EFFECT OF ORGANIC MATTER ON THE CURVES OF ION EXCHANGE pH RANGE

This paper deals with the effect of amino acid and humic acid on the ion exchange ratio (%)-pHS-shaped curves of the interactions between Cu, Pb, Zn, Cd and clays. The main results are: (i) Withthe increase of concentration of organic matters, S-shaped curve moves first to the left and then to theright, and △pH-(sh(L)) has a linear relationship with log (OB)_m. (ii) With the extent of a certain amountof organic matter, the sequence of △pH-(sh(L)) of heavy metals is Cu Pb Zn Cd, △pH-(sh(L)) has a linearrelationship with IogK_(OA). (iii) With the existence of different amino acids, the relationship between△pH-(sh(L)) of S-shaped curves of interaction between Cu and illite and IogK_(OA) for Cu and various aminoacids are linear. (iv) Quantitative explanations regarding the experimental phenomenon mentioned abovecan be written as the following equation: pH_((CIER))=-1/m{log[(α_1K_(OA)α_2(OB_m))/K_(RB_m)]?2}.(v) Discussion of the phenomenon of left-right shifts of S-shaped curve in terms of reaction mec     

THE MORPHOLOGY AND STRUCTURE OF ETHYLCYANOETHYL CELLULOSE IN STYRENE AND POLYSTYRENE

Ethyl-cyanoethyl cellulose ((E-CE)C)/styrene solution could form anisotropic system when the concentration was high enough. The (E-CE)C/polystyrene(PS)multiphase polymer could be obtained by radical polymerization of the styrene in the solution. The (E-CE)C/PS multiphase polymer maintained both the crystalline structure of the (E-CE)C and the amorphous structure of the PS. In the multiphase polymer produced from the isotropic solution, however, the (E-CE)C formed spherulites and spread in the PS amorphous phase. While, in the multiphase polymer produced from the anisotropic solution, the (E-CE)formed cylinderic crystalline aggregates. Moreover, the ordered lamellar texture was also observed in the multiphase polymer produced from the anisotropic solution.     

OXIDATION OF ALKYLBENZENE CATALYZED BY RUTHENIUM—POLYMERBOUND 2,2''''—BIPYRIDINE COMPLEXES

Oxidation of ethylbenzene, n-propylbcnzene and n-butylbenzene gives the corresponding ketones and alcohols in good yields by organic polymer supported low—valent Ru (Ⅱ) complexes under 1 atm. of air or oxygen at 100℃ in the absence of solvent. The calalytic selectivity to total ketone and alcohol ranged from 98.7％ to 100％. The polymer complex polymer—bipy—Ru—bipy (bipy=2, 2'—bipyridine) is very stable and can be reused for 5 times (each for 5h) without appreciable change in catalytic activity.