多嵌段聚氨酯表面组成的ESCA研究

多嵌段聚氨酯(SPU)是一种重要的医用高分子材料,其表面化学组成、表面结构,对血液相容性有直接关系。本文用电子能谱(ESCA)研究了两种链结构SPU的表面化学组成,其目的是了解表面组成与其本体结构及性能的关系,并将SPU表面组成与本体的相分离程度联系起来。实验结果表明:(1)在SPU-空气界面上O/N原子比大于其本体O/N原子比,即软段富集于表面;(2)分相程度高的SPU试样较分相程度低的试样其软段在表面富集得更多;(3)在50左右深度的表面层内相分离程度高的试样其O/N组成变化的梯度较大。     

聚醚聚酯嵌段共聚物共混物表面组成的ESCA研究

<正> 关于生物医用材料的微多相分离结构和适宜的亲、疏水性同它血液相容性间关系的研究已有不少文献报道。由于材料在使用时真正同血液相接触的只是材料的表面部分,因此材料的表面组成、结构和性质对它的血液相容性就具有更为直接的关系。对聚醚     

COMPOSITIONAL HETEROGENEITY OF ETHYLENE OXIDE-BUTYLENE TEREPHTHALATE SEGMENTED COPOLYMER*

A series of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with differentsoft segment length and hard segment content were synthesized. The compositional heterogeneity was studiedby solvent extraction. The results show that the compositional heterogeneity increases when soft segmentlength and hard segment content increase. The compositional heterogeneity is also reflected in thecrystallization behavior and morphology of soft and hard segment in EOBT segmented copolymer. The morecompositional heterogeneous the EOBT segmented copolymer is, the more different the morphology and thecrystallization behavior between separated fractions. Compared with ethylene oxide-ethylene terephthalate(EOET) segmented copolymer, compositional heterogeneity in EOBT segmented copolymer is weaker. Butthe compositional heterogeneity in EOBT segmented copolymer with long soft segment and high hardsegment content is still obvious.     

STUDIES ON POLYSILOXANE-POLYSTYRENE COMPOSITE LATEXES

Polysiloxane-polystyrene composite latexes were prepared by two-stage emulsionpolymerization. Polymerization of styrene in swollen polysiloxane latex particles were studied.Formation of simple polystyrene particle in the 2nd-stage polymerization depends on the particlesize of the lst-stage latex and the polymerization temperature. Polystyrene domains in thevulcanizates reinforce the silicone rubbers effectively.     

STUDIES ON ENHANCED CONDUCTIVITY OF STRETCHED CONDUCTING POLYMERS

A physical model of series of the conductivity on chain and the interchain conductivitybetween chains is proposed to explain enhanced conductivity of stretched conducting polymers.This model suggests that the enhanced conductivity for stretched conducting polymers might bedue to increasing of the interchain conductivity between chains along the elongation direction afterdrawing processes if the conductivity on chain is assumed much larger than that of the interchainconductivity between chains. According to this model, it is expected that the temperaturedependence of conductivity measured by four-probe method for stretched conducting polymers iscontrolled by a variation of the interchain conductivity between chains with temperature, whichcan be used to explain that a metallic temperature dependence of conductivity for stretchedconducting polymers is not observed although the conductivity along the elongation direction isenhanced by two or three orders of magnitude.     

STUDIES ON CRITICAL CONCENTRATION OF LIQUID CRYSTALLINE ETHYLCELLULOSE

Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than tensolvents were determined using both Abbe refractometer and polarized microscopy. Criti-cal concentration C_(crit) of forming liquid crystal phase decreased with increasing solubilityparameter δ of solvent until approaching the δ of polymer. Although the alcohols usedas solvents had the same variation rule, the critical concentration values of their solutionswere much higher, due to their excessive large hydrogen bond component of δ. The experi-ments of using mixed solvents which showed good linear relation between C_(crit) and δ alsoproved this rule. A technique of Transmission Optical Analysis was first used to estimatethe concentration dependence of critical phase transition temperature T_(crit) of EC, and aT-C phase diagram could be drawn.     

CHARACTERIZATION OF COMPOSITIONAL HETEROGENEITY OF SEGMENTED COPOLYMERS BY GPC TECHNIQUE

The GPC technique wth two detectors has been used to study the heterogeneity in compositionthard segment content) of a series of polyethylene terephthalate/polycaprolactone segmented copoly-mers. Improvement in data treatment has been made to avoid the difficulty resulted from the lake oflow molecular weight hard segment homopolymers. Results show that for each sample the moleculesof larger coil size in CHCI_3 usually have higher hard segment content. A parameter, the averagedeviation of hard segment content, has been proposed to characterize the heterogeneity in compositionof the samples. It is found that the heterogeneity of the samples increases with increasing theiraverage hard segment content.     

STUDIES ON THE POLYMERIZATION OF 2,2,6,6-TETRAMETHYL PIPERIDINYL METHACRYLATE

The radical homo-and co-polymerization of 2,2,6,6-tetramethyl piperidinyl methacrylate (TM-PM) with various initiators have been studied. It was found that, with azo-type initiators, the poly-merization proceeded readily, while with acyl peroxide initiators, the polymerization was inhibitedeffectively because of the formation of the stable TMPM-oxyl radical, identified by ESR. Thisobservation was further confirmed by the absence of inhibition effect on the addition of 2,2,6,6-tetramethyl 4-piperidinol to the polymerization system, whereas remarkable inhibition was observed onthe addition of the stable 2,2,6,6-tetramethyl 4-piperidinol N-oxyl radical. The reaction mecha-nism was discussed. We also found that when TMPM reacted with BPO in petroleum ether, N-benzoyloxy 2,2,6,6-tetramethyl 4-piperidinyl methacrylate was formed, and this novel compound has been characterizedwith IR, ESR, NMR and Mass Spectroscopy.     

STUDIES ON THE POLYMERIZATION OF β-CYCLODEXTRIN WITH EPICHLOROHYDRIN*

Different proportions of β-cydodextrin and epichlorohydrin were used to prepare a group of β-cyclodextrin polymers. The relationship between the reaction extent and the molar ratios of reactants was discussed according to the results of ~1H-NMR, ~(13) C-NMR spectra and elemental analysis. Especially, high resolution ~1H-NMR spectra were usd for studying the reaction active sites and the extent of reaction. The solubility of oil soluble drugs in water was largely improved in the presence of water-soluble β-cyclodextrin polymer.     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLYETHERS

Polyethers could form hydroperoxide under air-oxidation or photo-oxidation in the presence of H_2O_2. The scission of ether linkage induced by moderate oxidation was prevented by controlling the reaction time and hydroperoxide concentration. The oxidation rate was affected by the end groups of polyethers. The decreasing order of oxidation rate for various poly(tetramethylene ether) glycol derivatives having different end groups are as follows: poly(tetramethylene ether) glycol (PTMG)>poly(tetramethylene ether)acetate (PTMGAC) >poly(tetramethylene ether) phenyl carbamate (PTMGPC). The urethane end groups in PTMGPC increase the resistance toward oxidation. Polyether hydroperoxide reacts with ferrous ion or N,N-dimethyl toluidine (DMT) to form polymericoxy radical which then initiates the graft copolymerization of vinyl monomers at low temperature, and was devoid of homopolymerization. The copolymer after separation and purification was proved to be a graft one by IR analysis and elemental analysis.     

STUDIES ON THE KINETICS OF PROPYLENE POLYMERIZATION WITH THE COMPLEXTYPE TiCl_3 CATALYST

The active center concentration C_p, the rate constant k_p, and the activation energy of chain propagation E_p in the polymerization of propylene with complex-type TiCl_3-(C_2H_5)_2AlCl catalyst system were studied. The Mn was corrected by (?) value determined by GPC. The values thus obtained for C_p, k_p, and E_p at 50℃were 3.01 mol/mol Ti, 6.27 1/mol·sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl_3·AlCl_2 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher C_p of the former, but to a greater extent due to the increase of the k_p value.     

THE KINETICS OF CHARGE-ACCUMULATING PROCESS ON THE SURFACE OF PHOTOCONDUCTIVE COATING FILM

The charge-accumulating process of polymeric photoconductive coating film used in electro-photography as well as factors controlling the charging rate have been studied, and the characteriza-tion of charging process and kinetic equation have been established.     

STUDIES ON POLYMERIZATION KINETICS OF METHYL METHACRYLATE AT HIGH CONVERSION

The bulk polymerization of methyl methacrylate which was carried out in a metallic dilatometer and in a differential scanning calorimeter has been studied over the complete course of the reaction. An attempt was made to quantitatively express the relation on the onset of gel effect and the final conversion with polymerization conditions such as temperature, kinds and concentration of initiators. It was demonstrated further that the final conversion of polymerization in homogeneous ideal systems is only dependent upon the reaction temperature.     

STUDY ON SEGMENTED POLYURETHANE WITH MIXED SOFT SEGMENTS OF POLYCHLOROMETHYL METHYL SILOXANE AND POLYTETRAMETHYLENE OXIDE

Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.     

CHOLESTERIC LIQUID CRYSTALLINE CHARACTER ON THE SURFACE OF CHITOSAN/POLYACRYLIC ACID COMPOSITES*

The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface. Four kinds of perpendiculardisclinations, i.e. χ→τ→λ~+, χ→λ+τ~+, χ→τ+τ~+ and χ→λ~- +λ~+, were found in the composite films from SEMobservations. The smallest periodicity of lamellar-like structure (equals to half pitch) is 20～40 nm measured with AFM.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

聚醚氨酯薄膜表面性质的反相色谱法研究

本文报道了用反相色谱法研究多嵌段聚醚氨酯与几种低分子化合物的相互作用,测定了表征相互作用的热力学参数。结果表明,由ESCA证明表面软段富集的聚醚氨酯的反相色谱行为主要决定于富集层与探针分子的相互作用;苯及几种烷烃和聚醚氨酯的偏摩尔混合热和它的溶度参数与软段组分的溶度参数差值有关。     

STUDIES ON THE ORGANIC PEROXIDE-DITERTIARY AMINE INITIATION SYSTEMS

Radical polperization of methyl methacrylate (MMA) initiated with organic peroxide-ditertiaryamine binary systems was studied. Benzoyl peroxide (BPO), lauroyl peroxide (LPO), t-butyl hydro-peroxide (TBH), and t-butyl peroxybenzoate (TBPB) were used as organic peroxide components,aromatic ditertiay amine 4, 4′-tetramethyldiaminodiphenylmethane (TMDAPM) an d aliphatic di-tertiary amine tetramethylethylenediamine (TMEDA) were used as amine components. The polymeri-zation rate R_P, the overall activation energy of polymerization E_a, the rate equation of MMA poly-merization, and the end group of polymer formed were determined.     

STUDY ON PYROLYSIS OF POLYPHENYLSILSESQUIOXANE

X-ray photoelectron spectroscopy and Raman spectroscopy were used to determine the chemical change ofpolyphenylsilsesquioxane (PPSQ) during pyrolysis in flowing nitrogen. Two temperature ranges were found for pyrolysedPPSQ below and above 600℃, respectively. The former is related to the rearrangement of PPSQ backbone and the latterreflects that most of backbone structure of PPSQ might be broken down and unorganized. Carbon formed in carbonization ofPPSQ sample pyrolysed at 900℃ should be sp~3 bonded carbon with crystallite size effects or defects.     

ADSORPTION OF PROTEIN ON NANOPARTICLES

The adsorption of protein on nanoparticles was studied by using dynamic light scattering tomeasure the hydrodynamic size of both pure protein and nanoparticles adsorbed with differentamounts of protein. The thickness of the adsorbed protein layer increases as proteinconcentration, but decreases as the initial size of nanoparticles. After properly scaling thethickness with the initial diameter, we are able to fit all experimental data with a single mastercurve. Our experimental results suggest that the adsorbed proteins form a monolayer on thenanoparticle surface and the adsorbed protein molecules are attached to the particle surface atmany points through a possible hydrogen-bonding. Our results also indicate that as proteinconcentration increases, the overall shape of the adsorbed protein molecule continuously changesfrom a flat layer on the particle surface to a stretched coil extended into water. During thechange, the hydrodynamic volume of the adsorbed protein increases linearly with proteinconcentration.