最新刊期
卷 ， 期 2 ， 2002
-
LIVING RADICAL POLYMERIZATION AND COPOLYMERIZATION OF VINYL MONOMERS INITIATED WITH NOVEL INIFERTERS
摘要：Iniferter technique is an efficient and convenient method for preparation of well-defined vinyl polymers and copolymers,and developing novel iniferters is a continued theme in living radical polymerization area. In this review article,the progress of iniferter studies was summarized．Novel mono-functional thermal and photo iniferters,polymerizable iniferters,multi-functional iniferter and photo macroiniferters were designed,synthesized and used for preparation of well-defined end-functionalized polymers,block and graft copolymers．These thermal iniferters are diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS),diethyl 2,3-dicyano-2,3-di (p-tolyl) succinate (DCDTS)；photo iniferters are N-(p-tolyl)-N′-diethyldithiocarbamylacetamide (TDCA),ethyl N,N-diethyldithio-carbamylacetate (EDCA),n-butyl N,N-diethyldithiocarbamylacetate (BDCA),benzyl N,N-diethyldithio-carbamylacetaIe (BzDCA)；polymerizable iniferters are β-methacryloxylethyl 2-N,N-diethyldithiocarbamylacetate (MAEDCA),allyl 2-N,N-diethyldithiocar-bamylacetate (ADCA)；the multi-functional iniferter is diethyl 2,3-dicyano-2,3-di(p-diethyldithiocar-bamylmethyl) phenylsuccinate (DDDCS)；photo macroiniferters are α,ω-functionalized polyethylene glycol and polytetrahydrofuran macroiniferters．DCDPS and DCDTS not only can initiate MMA living polymerization at low temperature but also realize St living polymerization successfully in thermal iniferter area for the first time．MAEDCA bearing both vinyl group and DC group is used for synthesis of well-defined graft copolymer by two pathways．DDDCS bearing both thermal dissociated and photo dissociated chemical bonds,by alternative heating and irradiation sequence,can be used to synthesize a series of ABA triblock copolymers with controlled compositions and block chain length facilely,especially for PVAc-b-PSt-b-PVAc which cannot be prepared by using any other living radical polymerization methods.- 50
- |
- 9
- |
- 6
发布时间：2021-03-19
Feature Articles
- 摘要：Poly(L-lactide)／poly(DL-lactide)(PLLA/PDLLA) blends were prepared hy co-solution precipitation．They were molded into φ 3.2 mm rods by a method of fibrillated compression. The crystallization and miscibility of the blends were studied using differential scanning calorimetry(DSC)．The results showed that the PLLA component can crystallize in the process of co-solution precipitation．The melting temperature(Tm) and crystallinity (Xc) of PLLA component are identical with those of the pure PLLA until the content of PDLLA in the blends up to 30％；however, they are decreased obviously for the blend containing 50％ PDLLA．The Tm and Xc of the PLLA component in the rods scattered significantly and this may be attributed to their inconsistency in preparation．It was found that two glass transitions corresponding respectively to PDLLA and PLLA occurred in DSC heating scannings of the blends．This may indicate that PDLLA and the non-crystalline PLLA in the blends are immiscible．
- 5
- |
- 8
- |
- 1
发布时间：2021-03-19 - 摘要：The transesterification of poly(β-hydroxybutyrate) (PHB) and poly(ε-caprolactone) (PCL) was carried out by using stannous octoate as catalyzer in liquid phase．The effects of reaction conditions on the transesterification,including reaction temperature,reaction time and catalyzer content,were investigated．The sequence distribution,crystallization behavior and thermal stability of PHB-co-PCL copolyesters were studied by 13C-NMR,FTIR,DSC,WAXD and TGA．The results showed that the transesterification of PHB with PCL was confirmed to produce a block copolymer,and enhancing reaction temperature and increasing reaction time were advantageous to the transesterification. With the increase in PCL content in the block copolymer,the crystallization behavior of PHB-co-PCL copolyesters changed evidently．On the other hand,Lhe introduction of PCL segment into PHB chains did not change its crystalline structure；moreover,thermal stability of PHB-co-PCL copolyesters was a little improved in air,comparing with that of pure PHB．
- 7
- |
- 12
- |
- 3
发布时间：2021-03-19 - 摘要：Autocatalytic curing system of bisphenol-A epoxy resin(DGEBA)／trimercaptothioethylamine (TMTEA) was studied by means of differential scanning calorimetry (DSC)．The apparent activation energies obtained by Kissinger and Ozawa equations were relatively constant,namely,41.35 and 46.6 kJ／mol,and the curing reaction order and pre-exponential factor A of this system were calculated by using the theory of Crane et al．Meanwhile by in situ tracing of FTIR of absorption peak variations of the functional groups in the curing reaction process,the optimum curing reaction conditions were determined：Tgel=80℃,Tcure=120℃,Ttreat after=160℃．
- 2
- |
- 9
- |
- 13
发布时间：2021-03-19 - 摘要：A PS／PVC macroreticular bead polymer material was synthesized by interpenetrating polymerization of styrene into macroporous poly(vinyl chloride)bead,i．e．PS／PVC MR-IPN matrix．A series of the adsorption resins were prepared by further reaction of PS／PVC MR-IPN matrix with ethylenediamine,diethylenetriamine and triethylenetretamine．The resulting resins were applied to adsorb uric acid．The results show that these resins have higher sorption percentage,adsorption capacities and faster sorption speed for uric acid. The composition and properties of the resulting resins,as well as the influence factors for the eliminating uric acid character were investigated．
- 3
- |
- 8
- |
- 3
发布时间：2021-03-19 - 摘要：Mechanism of poly(dioxanone-co-glycolide) (PDG) sutures in vitro degradation was studied by DSC and X-ray diffraction and the surface morphology was studied with photography for the purpose of improving properties of absorbable sutures．The model of fiber structure,Swiss-Cheese model,provides the basis for the proposed degradation mechanism of PDG in vitro hydrolysis process. It is believed that the degradation of PDG proceeds through three main stages：the first stage occurs in the amorphous region,the second in the inter-microfibrillar non-crystalline region,the third in the crystalline part．The concepts of the three stages accord with the changes of PDG sutures during hydrolysis degradation. The properties of sutures decreased greatly from three to four weeks with respect to intrinsic viscosity,knot tensile strength and weight degradation,etc．The photography results show that the breaking modes are different for polydioxanone sutures (PDG) and PDG suture．PDS was broken by cross-section cracks and PDG was degraded via falling-off of large surface layers．
- 6
- |
- 8
- |
- 6
发布时间：2021-03-19 - 摘要：l,2-Dihydro-2(4-carboxylphenyl)-4-[4-(4-carboxylphenonxyl)phenyl]-phthalazin-1-one,a novel diacid monomer containing the phthalazinone moiety were synthesized based on the novel bisphenol 4-(4-hydroxyphenyl)-2,3-phthalazionone-l(DHPZ) synthesized by our research group．The novel diacid was used to synthesize polyamides with different acromatic diamines using Yamazaki method．The structure of monomers and polymers was studied through FT-IR,1H-NMR,the results showed that the structures of the monomers and polymers were in accordance with our design．The polymers have inherent viscosity of 1.17～1.50 dL／g(25℃,0.5％ in NMP) and are soluble in polar aprotic solvents such as DMAc,NMP etc．The Tgs of the polyamides were all above 280℃．The aromatic polyamide films had tensile strength of 72～87 MPa,elongation at break of 8％～13％ and tensile modulus of 0.8-1.0 GPa．The order of the coefficient of electrical resistance is 1014～1016．The result showed that the polyamides have the combination of excelllent thermal property,solubility,mechanical property and electrical resistance property．
- 39
- |
- 9
- |
- 8
发布时间：2021-03-19 - 摘要：A series of polyether esters thermoplastic elastomer,based on polyethylene glycol (PEG) as the soft segment and poly(butylene terephthalate)(PBT) as the hard segment,are synthesized by molten polycondensation and characterized by means of NMR,IR,DSC and mechanical testing．The influence of hard segment lengths on the properies of the copolymer is investigated in the case of the soft segment length remaining constant．It is observed that,first,the lenghth of hard segments calculated from 1H-NMR spectra is increased with the decrease of PEG content；secondly,four phases corresponding to the amorphous and the crystal phases of soft and hard segments coexist at certain temperatures；thirdly,the glass transition temperature (Tg) of the soft segment is increased,at the same time its molten point (Tm) and the degree of crystal (Wc) are decreased with the increase of the PBT segment length．Moreover,the inherent viscosity changes from 1.34 dL／g to 1.72 dL／g,and water uptake increases from 29.4％ to 104.4％ as the PEG content changes from 30％ to 80％(wt)．Although all copolymers are distinguished by a high elastic and plastic deformation and break at very high relative deformations,the sample of high PEG content displays the typical high elastic state,while the sample of low PEG centent exhibits neck-formation characteristics in the stress-strain curve．Obviously,the material’s properties under constant soft segment length can be tailored conveniently by changing the weight ratio of two components in formula.
- 3
- |
- 10
- |
- 24
发布时间：2021-03-19 - 摘要：The nanoscaled pores in porous polydivinylbenzene beads,prepared by the suspension polymerization of pure divinylbenzene isomers or industrial divinylbenzene in presence of toluene／liquid paraffin(2:1,V／V) as the mixed porogen,were characterized by nitrogen adsorption at 77 K and by scanning electron microscopy．It was found that the specific surface area and total pore volume were enlarged by increase of porogen amount．Among the polydivinylbenzene adsorbents with almost same total content of divinylbenzene monomers,only poly(m-divinyl-benzene-co-p-divinylbenzene) (1:1) adsorbent,other than poly(m-divinylbenzene) or poly(p-divinyl-benzene),possessed the largest specific surface area(726.3 m2／g) and total pore volume (0.6637 mL／g).From the mesopore size distributions of the polydivinylbenzene adsorbents according to BJH method,it was observed that mesopores were mainly distributed in the diameter range of 2～20 nm and a peak at about 5 am appeared．The result suggested that it was the mixed porogen to result in such mesopores in the polydivinylbenzene adsorbents．The mesopores could be directly observed on scanning electron micrographs．Micropore size distributions of poly(m-divinylbenzene) and poly(p-divinylbenzene),calculated on basis of HK method and SF method,revealed that there were lots of micropores in the range of 0.4～1.2 nm．Micropores would be the cavities formed owing to irregular aggregation of highly crosslinked polymeric chains．
- 39
- |
- 8
- |
- 9
发布时间：2021-03-19 - 摘要：Azo polymers were reported to be prepared from polystyrene through a nitration-reduction-diazotization-coupling (NRDC) reaction route. However,azo-coupling rates of the products were rather low because of the several steps of macromolecular reaction with low reaction yield in each step,or the obtained azo polymers could not be dissolved in any solvent due to the use of cross-linked polystyrene as precursor．Recently,photoresponsive azo polymers have become actively researched objects,but no PS-based azo polymers have been used as photo-responsive polymers so far due to above reasons．In this work,three kinds of soluble polystyrene-based azo polymers with high coupling rates have been synthesized through a modified NRDC procedure from polystyrene matrix．Both steps of the nitration and the reduction have nearly 100％ reaction yields. Macromolecular diazonium salts (MDS) prepared were reacted with N-alkyl aniline,substituted aniline and phenol type compounds through the azo coupling reaction．The intermediates and final products were characterized by 1H-NMR,IR and UV-Vis spectroscopy．Even though high coupling rates were obtained,diazonium salt groups could not be totally consumed due to the steric hindrance in the macromolecular reactions．The decomposition and cross-linking of these residual diazo groups were found to be the reason for losing of solubility of the products．The thermolysis process of the diazonium salt group was studied and a heating step of reaction mixture was added after the azo coupling reaction．In this step,the unreacted diazo groups were converted to phenolic hydroxyl groups,which was found to be essential for preparing soluble PS-based azo polymers．
- 39
- |
- 12
- |
- 8
发布时间：2021-03-19 - 摘要：The morphologies,mechanical properties and thermal stability of bisphenol A epoxy resin/4,4′-diamiodiphenysulphone(DDS)／liquid crystalline polymer(LCPU) blends were studied．The LCPU content was varied within 0 wt％～15 wt％. The cured materials were characterized by mechanical property test including impact strength,tnsile strength,bending strength,elastic modulus and elongation．The thermal stability,largely based on the decomposition temperature (Td),was investigated by the measurement of thermogravimetric analysis．SEM were used to study the morohology of the blends and the fracture surface of the cured materials．Compared wilh the unmodified system,the result showed that impact strength was enhanced to 3.6 times and bending strength was enhanced to 20％ for LCPU content of 5％,tensile strength was enhanced to 1.5 times for LCPU content of 10％,elasticmodulus was improved for 35％ and elongation percentage was improved fof 1.6 times for LCPU content of 7.5％,glass transition temperature(Tg) was increased 60℃ for LCPU content of 5％ and the decomposition temperature (Td) was increased 36℃ for LCPU content of 10％．SEM observation of the fracture surface of the impact specimen showed that the toughened fracture characters were obviously appeared for the blends．
- 5
- |
- 11
- |
- 23
发布时间：2021-03-19 - 摘要：The star-shaped C60-(styrene)-(sodium p-styrenesulfonate) copolymer [C60-poly(St-SS)] was synthesized successfully．The layer-by-layer self-assembly films from [C60-poly(St-SS)]／diazoresin were fabricated on mica by ionic attractive force．The crosslinking structure formed from the conversion of ionic bond to covalent bond after UV irradiation．The roughness and microtribological property of these films were investigated by AFM／ FFM,which provided insights into the prediction of load-bearing ability on C60-containing films．It was found that the microtribological properties are tightly related with the soft chain length and the layer number of the films．
- 2
- |
- 8
- |
- 3
发布时间：2021-03-19 - 摘要：With 1,2-dibromoethane and thiophenol as two initial chemicals,phenyl vinyl sulfoxide(PVSO) was synthesized through substitution of thiophenol,elimination of phenyl 2-bromoethyl sulfide and partial oxidation of phenyl vinyl sulfide．The anionic polymerizations of PVSO were carried out with different naphthalene-alkaline metal initiators in THF at-78℃ under inert atomosphere．With succinic anhydride as the terminator,monodispersed telechelic polymers of PPVSO with different molecular weight were obtained．The functionality of PPVSO was determined by the methods of FTIR and titration and its value is more than 1.60．The thermal elimination of PPVSO under vacuum resulted in monodispersed telechelic polyacetylene with metal alkaline carboxylate as end groups．PPVSO WaS converted to poly(phenyl vinyl sulfone) by further oxidation．
- 2
- |
- 10
- |
- 0
发布时间：2021-03-19 - 摘要：Calix[n]Nd／MgBun2／HMPA is an effective catalytic system for the synthesis of the ultra-high molecular weight polystyrene (UHMWPS)．The catalytic activity of different Calix[n]Nd complex decreases in the following order：Calix[6]Nd＞Calix[4]Nd＞Calix[8]Nd．It shows that the aging of catalyst plays an important role on catalytic activity．The optimum conditions are as follow：Mg／Nd=20.0(molar ratio),HMPA／Mg=1.0(molar ratio),and aged 2.5 h under 50℃．The study of influence of solvent shows that toluene is a good solvent．The polymerization result shows that the conversion is over 80％ at 50℃,45 min．The kinetics of styrene polymerization using Calix[6]Nd-20MgBun2-20HMPA in toluene were investigated by weight method．It was found that the rate of polymerization is first order with respect to both monomer (St) and Calix [6] Nd concentrations．According to Arrhenius equation,it was found that polymerization activation energy is 41.7 kJ／mol．GPC characterization of obtained polymer shows：Mw=21.0×105,MWD=1.61．1H-NMR spectra of UHMWPS shows that the content of syndiotactic triad is 81％.
- 34
- |
- 11
- |
- 7
发布时间：2021-03-19 - 摘要：LB films of polyimide with promellitic dianhydride (PMDA) and 4,4′-diaminophenylether (ODA) structure were fabricated by so-called “precursor” method,and SiC ultrathin films were obtained by pyrolyzing the polyimide LB films at a high vacuum of 1×10-5 mbar and a temperature of 1000℃．In order to study the mechanism of this pyrolysis process,X-ray photoelectron spectroscopy (XPS) technology was used to study the polyimide LB film and to trace the pyrolysis process of the LB film in-situ．By probing the polyimide LB film from different angles,it was found that in the LB films,the elements were much evenly distributed,the quantitative analysis of the elements was also in very good agreement with the theoretical value．The in-situ trace showed that at about 500℃ the molecules of polyimide decomposed to amorphous carbon；in the meantime,some small molecular weight gases were given out；the remained skeleton C in the LB film began to react with Si from substrate to form SiC at about 670℃．Higher temperature and longer time would be helpful for the reaction of SiC formation to proceed thoroughly．It also found that at lower temperature,the substrates were oxidized to SiOx (x＜2) by the oxygen it absorbed,but at higher temperature,the SiOx was reduced to SiC by the skeleton C in the LB films．Auger Electron Sputting (AES) spectrum indicated that the atoms of C and Si distributed gradiently in the SiC films,suggesting the mutually diffusion mechanism in the SiC formation．
- 3
- |
- 12
- |
- 0
发布时间：2021-03-19 - 摘要：Polystyrene doped with mixed rare earth triisobutoxide has been prepared by in-situ bulk polymerization. The modified polystyrene (PS) has been characterized by FT-IR,UV-Vis,fluorescence spectra (FS),dynamical mechanical thermal anaylsis(DMTA) and the impact strength of PS materials was determined before and after the modification．The results showed that coordination interaction exists between rare earth ion with phenyl in the modified PS. The modified PS materials are soluble in common organic solvents,such as benzene、chloroform、tetrahydrofuran and N,N-dimethylformamide,which make them useful for forming films．Indicated by FS,the fluorescence strength of the modified PS is higher than that of pure PS．By the DMTA curves of PS materials,it is indicated that the glass transition temperature(Tg) of the modified PS decreases with increasing rare earth content and there is a broad β-transition peak at -70℃．Moreover,the peak of loss modulus at low temperature and the impact strength are enhanced considerably．Therefore it can be concluded that the mixing of rare earth triisobutoxide has good toughening effect for polystyrene．
- 42
- |
- 9
- |
- 2
发布时间：2021-03-19 - 摘要：A new class of phenolic-like thermosetting resins based on the ring-opening polymerization of naphthoxazine precursor exhibits some unique properties,including：no by-product releasing during curing reactions；near-zero shrinkage and excellent mechanical properties．Polynaphthoxazines-clay hybrid nanocomposites were prepared from 1,5-dihydroxynaphthalene,aniline,formaldehyde and different proportion montmorillonite(MMT) by in-situ reaction in ethanol．1H-Nuclear Magnetic Resonance(1H-NMR)、X-ray Diffraction Analysis (XRD)、Thermogravimetry (TGA) and Transmission Electron Microscopy (TEM) were applied to characterize the nanocomposites．1H-NMR spectrum of naphthoxazine from the nanocomposites was identical to that of the pristine naphthoxazine,indicating the presence of MMT didn’t change the chemical structure of the product．The spaces of silicate layers of montmorillonite in the composites were investigated by using X-ray diffractometer．It was found that exfoliation structure was formed after in-situ synthesis reaction and was remained after being cured．The TEM results suggested that an exfoliated polynaphthoxazine-montmorillonite nanocomposite was successfully achieved. Dynamic TGA showed that only very small amount of clay is effective to improve the weight residues for nanocomposites．The char yield at 700℃ increased by ca．10％ with 5 wt％ MMT content in the nanocomposite and reached 65％．The confined crystallization behavior of the system was discussed．
- 33
- |
- 9
- |
- 2
发布时间：2021-03-19 - 摘要：PUI block copolymers with three diferent soft segments were synthesized and characterized．FTIR spectroscopy studies confirmed the characteristic absorption of polyurethane-imide main chain structure of all PUI samples．DSC analysis revealed that the values of the glass transition temperature of hard segments rich phase (Tgh) were increased with all increase of soft segments length for the same kind soft segment．DSC results additionally support that with an increase of soft segment length,the soft and hard segments phase compatibility was decreased and the soft-hard block phase was more separable．TGA revealed that the thermal stability of different soft segment PUI was in the order of PEPA-PUI＞PEG-PUI＞PPO-PUI,and dynamic mechanical thermal analysis (DMTA) of PUI samples also showed that the storage energy modulus platform dropping is not remarkable from 50～200℃,this result proved that thermo-plastic PUI elastomer samples may have good thermal mechanical properties,which was found to be improved by increasing the hard segments content of PUI systems．
- 30
- |
- 8
- |
- 4
发布时间：2021-03-19 - 摘要：A detailed research on poly(AA-b-DXL) networks as a continued paper was reported here．The copolymer networks poly(AA-b-DXL) as a combined two hydrophilic parts of PDXL and PAA,not only possess the pH sensitivity,but also can swell in both water and organic solvents．The effects on the swelling behavior of hydrophilic poly(AA-b-DXL) networks were deeply reported．The results showed that the solubility parameters of solvents and constituents of the networks have a great influence on the swelling behavior of poly(AA-b-DXL) networks．It means that the networks can reach high swelling degree when the solubility parameter of the solvent is close to either that of the PDXL segments or that of the PAA segments．A micro-phase separation structure was observed and explained．By SEM analysis,the microphase conformation can be clearly observed．No obvious microphase separation was observed when the PDXL content is much higher than that of the PAA．With increase of PAA content in the network to 50 wt％,there is an obvious phase separation．
- 32
- |
- 8
- |
- 0
发布时间：2021-03-19 - 摘要：The engineering polymer alloys of syndiotactic polystyrene (sPS)／polyester (PET)／zinc salt of sulfonated syndiotactic polystyrene ionomer (SsPS-Zn) have been prepared and the mechanical properties,misibility,thermal behavior and morphology of alloys were investigated．When sPS/PET/SsPS-Zn=85／15／2 (weight ratio),the unnotched Izod impact strength of alloy reached maximum value of l0.6 kJ／m2,which was about 2.5 times of the pure sPS,while tensile strength and flexural strength were still higher than that of pure sPS．TMA showed that addition of SsPS-Zn,the alloys had better thermal resistance．Results of DSC showed that the melting temperature of sPS was the same compared with pure sPS．The initial crystallization temperature and the temperature at maximum crystal velocity of sPS were all higher than that of pure sPS and did not change with increasing content of SsPS-Zn. Crystallinity changed downward slightly and crystallizing velocity decreased with increasing content of SsPS-Zn．The melting temperature,the initial crystallization temperature and the temperature at maximum crystallizing velocity of PET decreased with increasing content of SsPS-Zn．DMA showed that all alloys have one glass transition temperature (Tg)．Tg and the half peak width was lowest on addition of 2 parts of SsPS-Zn．The storage modulus at room temperature was highest on addition of 2 parts of SsPS-Zn,too．SEM displayed on addition of 2 parts SsPS-Zn,the dispersion dimension of PET was decreased and more evenly,while on addition of 6 parts SsPS-Zn．it increased．
- 3
- |
- 9
- |
- 1
发布时间：2021-03-19 - 摘要：Two series of semifluorinated fluorocarbon diblock copolymer P(BMA-b-FAEM) have been synthesized by atom transfer radical polymerization (ATRP),and the ATRP of fluorinated monomer FAEM initiated by bromine-endcapped PBMA was studied in detail．GPC data showed the block copolymer molecular weight increased linearly with fluorinated monomer conversion．And efficient block copolymer formation had been demonstrated by FTIR and H-NMR,which is indicative of good living character. Combining the GPC and fluorine-element analysis,the molecular weight of fluorinated copolymer was calculated more accurately,the experimental results matched the design very much. Measurements on the thin (perfluoroalkyl) ethyl acrylate-containing acrylic polymer films showing low critical surface tensions and low dispersion force contributions to the surface energy indicated the presence of the fluorinated block at the surface. The results showed that the water and oil repellency increased with the fluorine content in the diblock copolymer. After annealing at different temperatures or different time,the water and oil repellent properties of diblock copolymer were increased to approach maximum values. These phenomena prove the propensity of polymer for fluorine enrichment at air-polymer surface. The sample BMA96 FAEM3.1 (γc=18.7) with incorporation of 10.6wt％ (perluoroalkyl) ethyl acrylate FAEM has obvious water and oil repellent property．Water and paraffin liquid contact angles for the sample BMA96 FAEM3.1 were larger than 100 and 75 degrees respectively,it could be estimated that surface tensions of these polymers were comparable to that of PTFE (γc=18.5). The block copolymer surface showed notable hydrophobic and lipophobic property.
- 34
- |
- 9
- |
- 27
发布时间：2021-03-19
Research Article
- 摘要：Free volume theory was applied to the diffusion mechanism of drug through semi-crystalline ethylene- vinyl acetate (EVA) copolymer．According to free volume theory,drug diffused through semi-crystalline EVA via vinyl acetate segments of the copolymer,and the dependence of D(D：diffusion coefficient of drug through EVA)on a (a：vinyl acetate content of copolymer；a＜0.5) could be described as ln(D)=A1-A2/a(A1,A2：constant)．This was demonstrated by experimental data from several references.
- 6
- |
- 10
- |
- 1
发布时间：2021-03-19 - 摘要：The UP-PER-UP blocked copolymer was prepared by the reaction of unsaturated polyester(UP)and polyepoxy resin(PER)under suitable conditions．The modified photosensitive resin was formed after the addition of the active monomers into the copolymer．The UV-cured process of the resin was investigated by means of FTIR spectrum and the properties of the UV-cured coat were characterized in terms of TG／DTA and other analysis．The resuIts indicated that the UV-cured resin showed the advantages of both unsaturated polyester resin and polyepoxy resin．The base-resistant ability,thermostability and surface hardness of the resin were greatly improved．The volume shrinkage of the sample was lowered from 7％ to 0.8％ and the adhesion power on substrate was increased. Thus the applications of unsaturated polyester resin were widely promoted．
- 3
- |
- 9
- |
- 6
发布时间：2021-03-19 - 摘要：A liquid crystalline block copolymer (BCPE) was synthesized from bis-phenol-A epoxy oligomer and liquid crystalline polyester (PBHT) which was prepared from polyhexamethylene-bis-(4-oxybenzoates) and terephthaloyl dichloride by solution polymerization．The intrinsic viscosity (ηinh) of the polymers was determined using an ubbelohde viscometer in phenyl hydroxide／1,1,2,2-tetrachloroethane mix solvent (1:1) at 30℃,and the results showed that the ηinh values of PBHT and BCPE are 0.16 dL／g and 0.46 dL／g respectively．FTIR analysis identified the reaction between bis-phenol-A epoxy oligomer and PBHT．The crystalline properties of polymers were investigated with DSC and WAXD,and the results found that the crystallinity of BCPE is inferior to that of PBHT due to addition of amorphous epoxy．Thermotropic liquid crystalline nematie phase textures of polymers were observed under a polarizing microscope with hot stage．
- 4
- |
- 10
- |
- 7
发布时间：2021-03-19 - 摘要：A novel exfoliated silicone rubber／clay nanocomposite has been synthesized by hydroxyl-terminated polydimethylsiloxane and organoclay．HTAB and TPAC were used as swelling agents to treat Na-montmorillonite for forming organoclay．The organoclay and nanocomposite were confirmed by X-ray diffraction (XRD)．The d-spacing in TPAC-mont is 4.96 nm,being larger than that of the HTAB-mont．The mechanical properties of the nanocomposites have been measured by tensile testing machine．The results proved that the nanometer-scale silicate layers of TPAC-mont were completely exfoliated in silicone rubber matrix in the cases of 1％ to 10％ TPAC-mont content．The nanocomposites exhibit markedly improved mechanical properties and thermal stability when compared with the pure polymer or conventional aerosilica-filled silicone rubber．A 200％～300％ increase in the tensile strength and a 100％ increase in the elongation at break were found for TPAC-mont／silicone rubber as compared to that of pure silicone rubber. The reinforing and intercalating mechanism of silicate layers in silicone rubber matrix were discussed．
- 2
- |
- 9
- |
- 3
发布时间：2021-03-19 - 摘要：The morphological evolution of the latex particles obtained by VAc／BA two stage emulsion polymerization was studied．The designs of two group experiments were as follows：VAc as seed,BA was added in starved or overflown condition．The inverted core-shell composite latex particles,with PVAc as shell and PBA as core,were found in overflown condition,however,the core-shell composite latex particles,with PVAc as core and PBA as shell were found in starved condition．When the core-shell composite latex particles in different time in starved condition was kept to reaction end,the morphology of the latex particles inverted．Comparing with the previous work in literature,this paper can provide better and more complete understanding about the morphological evolution of the latex particles in the process of seeded emulsion polymerization of VAc／BA．The photos of TEM of morphology of the latex particles in the process under two conditions and temperature being kept constant were obtained．From viscosity,the existed paradoxical views about the morphology of the latex particles on VAc／BA can be explained in a better and more complete way．
- 36
- |
- 10
- |
- 5
发布时间：2021-03-19
Research Bulletin
- Postal code：100190
- Tel：010-62588927 Email：gfzxb@iccas.ac.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备05002797号-8
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0