STUDIES ON POLY(ETHYLENE TEREPHTHALATE)-POLY(TETRAMETHYLENE ETHER) MULTIBLOCK COPOLYMER.Ⅱ.THE MOLAR SEGMENT MASS AND MOLAR MASS

The molar segment mass, weight-average molar mass, and molar mass distribution of a poly-(ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample were determined by the methods of proton nuclear magnetic resonance, low angle laser light scattering, and gel permeation chromatography.     

STUDIES ON ULTRASONIC GRAFTING OF POLY(VINYL ACETATE) WITH POLY(ETHYLENE OXIDE)

The ultrasonic degradation of poly(ethylene oxide) and poly(vinyl acetate) in benzene solution, and grafting reaction of poly(vinyl acetate) with poly(ethylene oxide) were studied. It is found that the chain-scission reactions follow the course suggested by D. W. Ovenall. The structure of the copolymer was identified by IR, NMR and DTA, showing that the copolymer prepared is a graft copolymer mainly. The copolymer formed by irradiating 1% PEO/PVAc solution (PEO/PVAc:1/1 by weight) for a period of 10 rain at 18.2 kHZ, with 2.0 A input current on reversed main circuit, amounts to 10.5%.     

STUDIES ON EPOXY RESINS MODIFIED WITH POLY (BUTYLENE TEREPHTHALATE)-b-POLY (TETRAMETHYLENE GLYCOL)

Poly(butylene terephthalate )-b-poly (tetramethylene glycol) (PBT-b-PTMG) was usedas rheology modifier for the epoxy resin. The segmental copolymer formed spherulites inthe epoxy medium. This copolymer was very effective in endowing yield stresses to theliquid resin. The PTMG segment brought in a lowering of the dissolution temperature ofthe spherulites in the epoxy gel. The cured resin with PBT-b-PTMG as modifier was two-phase materials. The rheology modifier improved the mechanical properties of the curedresin as well. The flexible PTMG segments, however, were not in favour of the tougheningeffect of the modifier. This was attributed to the large domain size of the dispersed phase.     

STUDIES ON ULTRASONIC ABSORPTION AND VISCO-RELAXATION OF POLY (ETHYLENE GLYCOL) AQUEOUS SOLUTIONS

Ultrasonic absorption and velocity measurements were made on aqueous solutions of poly (ethylene glycol)(PEG)of different molecular weights and concentrations, using a pulse sender-receiver ultrasonic generator, Measurements were obtained at a frequency of 2MHz. , and a temperature of 293 K. The results show a linear increase of the Values of velocity, density and viscosity with increase of molecu lar weight and concentration of PEG. On the contrary, the attenuation values decreased with increase of molecular weight and concentration of PEG. A mathematical equation correlating relaxation amplitude and molecular weight of the polymer is suggested. This was applied to calculate the molecular weights of unknown samples of PEG from their measured relaxation amplitude. The results obtained were in good agreement with those obtained from osmometry.     

A STUDY ON POLY (ETHYLENE OXIDE)/POLY(VINYL ACETATE)BLENDS

Melt blends of poly(ethylene oxide) (PEO) and poly(vinyl acetate (PVAc) were prepared andstudied by Torsional Pendulum Analysis (TPA) and Fourier Transform Infrared (FTIR). Two glasstransitions were found in these blends. The lower T_g corresponds to the segmental motion in thepure PEO. The dependence of the position and broadness of the higher T_g on composition of theblends indicates that the two components are compatible in the amorphous phase with micro-hetero-geneity. These T_g values observed from mixed PVAc/PEO phase are much higher than that calculatedfrom Fox equation. The comparison of the blends quenched and annealed from melt implies thatPVAc mixed with PEO at the segmental level on molten state and the deviation of T_g values fromFox equation could be due to variation of the blend's composition by crystallization of part of thePEO component. Further indication that the blends are compatible down to the level of chain segments and thatthere are specific interactions between PVAc and PEO molecules comes from the analysis of FTIRspectra of the blends and the solution of PVA in diethylene glycol dimethyl ether.     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.     

STUDIES OF THE CRYSTALLIZATION BEHAVIOR IN THE CRYSTALLINE/AMORPHOUS POLYMER BLENDS: POLY(ETHYLENE OXIDE)/POLY(METHYL METHACRYLATE) AND POLY(ETHYLENE OXIDE)/POLY(VINYL ACETATE)

The crystallization process of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA)and PEO/poly(vinyl acetate) (PVAc) blends has been characterized by Fourier Transform Infrared(FTIR) spectra in conjunction with Differential Scanning Calorimeter (DSC) measurements. Thecrystallinity of PEO varies consistently with PEO content in PEO/PVAc blends and the PEO/PMMAblends containing 50 wt% or less PMMA. For the PEO/PMMA blends containing 60 wt% ormore PMMA, the crystallinity of PEO decreases more than PEO content but develops with crystal-lization time. These results can be explained in terms of difference between the crystallization tem-perature (T_c) and glass transition temperature (T_g) of the blends as a function of content of amorphouscomponent.     

STUDIES ON REGULARITY OF POLY PHENYLSILSESQUIOXANE CHAINS

IR and ~(29)Si NMR were used to determine the structures of ladderlike polymer polyphenylsilsesquioxanes (PPS). It was found that PPS with lots of defects had a wide and strong absorption band in 1000—1400 cm~(-1) with only one sharp peak at 1137 cm~(-1) while two peaks (1130 and 1045 cm~(-1) were observed for PPS with perfect ladderlike structure. Branching and crosslinking of PPS lead to the reduction of 1045 cm~(-1) peak. ~(29)Si NMR spectra, however, showed two peaks (δ=-78 ppm and -87 ppm when δ_(HMDS)=0 ppm) for defective or branched PPS. The -87 ppm peak is related to the ladderlikely constructed Si atoms and -78 ppm corresponds to defective Si atoms. PPS with defects less than 0.1% chain units was obtained by azeotropic polycondensations.     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLY(ETHER-URETHANE)

A new method of graft copolymerization of acrylamide (AAM) on poly(ether-urethane) (PEU) which was prepared from poly(tetramethylene ether) glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI) and ethylene diamine or butanediol extender was investigated. Hydroperoxide group was first introduced onto the surface of PEU through photo-oxidation in the presence of hydrogen peroxide, then it was reacted with ferrous ion or N,N-dimethyl toluidine (DMT) to initiate AAM graft copolymerization on PEU surface. The graft reaction could be carried out effectively at low temperature. The formation of graft copolymer has been verified by its water absorption % and the scanning electron microscopy photographs. Some model compounds of PEU soft segment and hard segment were synthesized in order to clarify the site of graft reaction. The results of oxida-tion and graft copolymerization of model compounds showed that this graft copolymerization possesses higher selectivity, and it takes place predominately at the polyether segments, because the ether linkage in soft segment is very sensitive to oxidation and can form hydroperoxide easily. Thus, the grafting site appears to be at α-carbon of the ether linkage.     

CRYSTAL PACKING OF POLY(ETHER KETONE KETONE)

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SYNTHETIC STUDIES ON BLOOD COMPATIBLE BIOMATERIALS Ⅲ. SYNTHESIS, CHARAC-TERIZATION AND ANTITHROMBOGENICITY OF DIMETHYLDIPHEN YLPOLYSILOXANE/POLY (OXYTETRAM ETHYLENE)-POLYUREA SEGMENTED COPOLYMERS

A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α, ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared by means of basic ring-opening copolymerization of octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and 1, 3-bis (γ-aminopropyl) tetramethyl disiloxane. The relationships between the diphenylsiloxy contents and the properties of APMPS, including refractive index, glass transition temperature, solubility parameter as well as thermal stability, were investigated; meanwhile, the thermal stability, dynamic mechanical properties, mechanical properiesas well as the antithrombogenicity in vitro of the PSPEU were also revealed.     

STUDIES ON THE EXCIMER FLUORESCENCE OF POLYPHENYL GLYCIDYL ETHER AND POLYNAPHTHYL GLYCIDYL ETHER

Polyphenyl glycidyl ether (PPGE) and polynaphthyl glycidyl ether (PNGE) have beensynthesized by cationic polymerization and their structures characterized by carbon 13 NMRand 1R, etc. The fluorescence spectra of PPGE, PNGE and their corresponding monomersPGE, NGE as model compounds have been studied. In dilute solutions at room temperature,only monomer fluorescence of the chromophore is observed. Comparison between the spectraobtained from dilute solutions, concentrated solutions and solid film shows that there is excimeremission when polymer chains in solution or in film are sufficiently close to each ocher.From the concentration dependence of the excimer emission, further evidence is obtained forthe existence of interchain excimer interaction in these polymers.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS:POLY (ARYLENE TEREPHTHALATECO-HEXAMETHYLENE TEREFHTHALATE)

A series of copolyesters based on terephthaloyl chloride, hexamethylene glycol and hydroquinone or chlorohydroquinone were prepared. The copolymers showed composition-dependent liquid crystalline properties as verified by visual observation of stir-opalescence, polarizing microscope and DSC. The copolyesters with aromatic diol contents over a certain extent (x≥0.2) were thermotropic with wide liquid crystalline temperature ranges. Comparing with the copolyesters based on butylene glycol or ethylene glycol, the minimum fraction of aromatic diol (x value) used to get the liquid crystallinity for all these copolyesters is around 0.2 regardless of the chain lengths of aliphatic glycols. ~1H-NMP studies revealed that copolyesters have microstructure of block sequence distribution and the mesogenie segments shorter than triad with three phenyl nuclei will not provide the liquid crystallinity.     

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-     

FOURIER TRANSFORM INFRARED STUDIES OF POLY (ETHYLENE TEREPHTHALATE) FILM IN THE GLASS TRANSITION REGION

Three specimens from a solution-cast poly (ethylene terephthalate) (PET) film, one being liquid-N_2 quenched from 92℃(Q), one being slowly cooled from 92℃(SC) and one being quenched and sub-T_g annealed at 67℃(AN), have been studied by specimen difference spectra Q-SC and AN-Q and temperature difference spectra T-70 and T_2-T_1 for every 2℃steps on heating to 90℃at 2℃/min. SC and AN showed more gauche conformers than Q. That means that the PET chain has more trans conformers at higher temperatures and some of these are frozen during quenching through T_g. A band at 1340 cm~(-1) has been found to be complex containing overlapping bands reflecting trans in crystalline regions and trans in amorphous regions. The temperature difference spectra on heating through T_g showed that the spectral changes in Q are gradual while a rather abrupt change occurs in AN at 80—82℃for the bands at 1340, 1042 and 1020 cm~(-1). No new conformational structure or new vibrational mode is involved. A kind of locking mechanism is suggested which hinders the molecular vibrational changes in AN below T_g until a sudden release occurs at T_g. These locking sites can be nothing else than sites of tighter local packing of chain segments. Consequently it is believed that inter-chain van der Waals attraction energy plays a dominating role in the volume relaxation and sub-T_g annealing of quenched amorphous polymers.     

STUDIES ON CROWN ETHER CYANINE DYES (X). THE SYNTHESIS OF BENZOXAZOLE CROWN ETHER CYANINE DYES

A simple method for synthesis of benoxazole crown ether cyanine dyes is described.     

POLYCAPROLACTONE-POLY (ETHYLENE GLYCOL) BLOCK COPOLYMER Ⅲ DRUG RELEASE BEHAVIOR

The drug release behavior of degradable polymer--polycaprolactone-poly (ethyleneglycol)block copolymer(PCE) in vitro was investigated by using 5-Fluoro-uracil (5-Fu) asa model drug under a condition of pH 7. 4 at 37C. It is found that the release rate of 5-Fufrom PCE increased with increasing polyether content of the copolymer. The results showthat the increasing polyether content of the copolymer caused increasing hydrophilicity anddecreasing crystallinity of the PCE copolymer. Thus, the drug release behavior and thedegradable property of the PCE can be controlled by adjusting the composition of thecopolymer.     

~(13)C NMR STUDIES ON DYNAMICS OF POLY (n - ALKYL METHACRYLATES)

The dynamics of a series of poly(n-alkyl methacrylates) is investigated by means of ~(13)C spin-lattice relaxation experiments. The results show that the dynamics has the polymer property dependence.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS——POLY (ARYLENE TEREPHTHALATE-CO-BUTYLENE TEREPHTHALATE)

A series of copolyesters based on bis(4-hydroxybutyl) terephthalate, terephthaloyl chloride andvarious aromatic diols (i.e. hydroquinone, chlorohydroquinone, bromohydroquinone or dihydroxybi-phenyl) was prepared. ~1H-NMR studies revealed that the monomer units had microstructures closeto random distribution in the chains. The copolymers showed composition-dependent liquid crystal-line properties as verified by visual observation of stir opalescence, polarizing microscope, DSC andX-ray diffration. The copolyesters with aromatic diol contents over a certain extent (for chloro-hydroquinone m≥0.33) were thermotropic with wide liquid crystalline temperature ranges. Theintroduction of chlorohydroquinone into the copolyesters could gradually destroy the crystallinityof the polymers but retain the liquid crystalline characteristics.     

THE DOUBLE MELTING PEAKS OF POLY(ETHYLENE TEREPHTHALATE)

Three sets of PET samples, comprising original (undrawn), uniaxially drawn and biaxially ones, after annealed at 230°, 240°and 250℃respectively, were subjected to DSC thermal analysis, X-ray diffraction analysis and IR analysis. The results indicate that the phenomenon of double melting peaks during DSC analysis is due to the partial melting and recrystallization of the crystallite at the moment of thermal scanning. The lower temperature peak, which varies slightly according to annealing condition, corresponds to the melting of imperfect crystallite, and the higher temperature peak corresponds to the melting of better organized crystallite. In the course of temperature scanning, the unit cell parameters of PET remains unchanged while the crystals turn to better crystal lattice, greater crystal size and more regular folding.We also found that there is a slight reduction in crystal size between the two melting peaks, and an explanation is suggested for this phenomenon.