最新刊期
卷 ， 期 3 ， 2001
- 摘要：Atom transfer radical polymerization(ATRP)is an efficient way for living radical polymerization ．Reverse ATRP was first reported by Matyjaszewski in 1995 and it is a development and improvement of conventional ATRP．In this review article,we summarize the progresses of reverse ATRP studies in our research group,especially the initiating systems consisting of thermal iniferter and metalic complex catalyst,that are the 1,1,2,2-tetraphenyl-1,2-ethanediol(TPED)／FeCl3／triphenylphosphine(PPh3),diethyl 2,3-dicyano-2,3-di(p-tolyl)succinate(DCDTS) or diethyl 2,3-dicyano-2,3-diphenylsuccinate(DCDPS)／CuCl2／bipyridine(bipy)and DCDPS／FeCl3／PPh3 initiating systems．Using these initating systems, well—defined PMMA and PSt with high molecular weights and quite narrow molecular weight distributions were successfully synthesized．1H—NMR analysis revealed that the resultant polymers were end functionalized by α-H[or α-(CN)(C6H5)(CO2C2H5)]and ω-Cl groups ．The polymers with ω-Clgroups can serve as macroinitiators to proceed chain extension reactions with fresh monomer and block copolymerization with a second monomer．The polymerization mechanisms belong to reverse ATRP．
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发布时间：2021-03-19 - 摘要：The syntheses of the homopolymers and diblock copolymers by adding dithioester as chain transfer agent．First a series of monomers：methyl methacrylate (MMA),butyl methacrylate (BMA),methyl acrylate (MA),ethyl acrylate (EA),butyl acrylate (BA),and styrene (St) were polymerized in bulk by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization．AlI of these homopolymers (PMMA、PBMA、PEA、PBA、 PMA、PSt) have the controBable polymerization characteristics,the polydisporsity index(PDI)is narrow(1.08～1.30)．At the same reaction conditions the rate of polymerization of the methacrylate is the fastest,styrene is slower,acrylate is the slowest．The higher the reaction temperature,the faster the polymerization rate．The effects 0f the molar ratio of chain transfer agent to initiator on polymerization and the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were discussed．The diblock copolymers have the characteristics of the controlled／living radical polymerization,that is to say that the real molecular-weight of these copolymers is similar to the theoretical molecular-weight,and the polydispersity index is less than 1.80．When the molar ratio of ABIN to CTA is ranged from 1:3 to 1:6,the copolymers with PSt as the first block also have characteristics of the controlled／living radical polymerization．The 1H-NMR spectra of the homopolymer (PMMA) and copolymer (PMMA-b-PEA) showed that the synthesized polymers have functional groups,dithioester,at the end of these polymers．
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发布时间：2021-03-19 - 摘要：Cationic polymerization of 1,3-pentadiene initiated by trimethylsilyl compounds,trimethysilyl trifluoromethanesulfonate (TMSOTf) or trimethysilyl chloride (TMSCl),in combination with TiCl4,SbCl3 or AlCl3,was carried out in n-hexane or in toluene．The polymer yields are greatly increased by the addition of TMSOTf or TMSCl．However,the introduction of TMSOTf or TMSCl gives a drop of polymer molecular weight．Kinetic results demonstrate that the polymerization initiated by the composite initiating systems is faster than that induced by Lewis acids alone．Various electron donors (such as ethers,ketones) were used to mediate the initiating systems．Adding diphenyl ether could increase both polymer yield and molecular weight．Structural evidences illustrate that the polymerization is initiated by Lewis acid in combination with HCl or HOTf,which are resulted from hydrolysis of TMSCl or TMSOTf by water contained in the system．
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发布时间：2021-03-19 - 摘要：The structural transitions and free volume properties for two kinds of linear polyurethane prepared with polybutalene adipate polyol and polycaprolactone polyol (PBU and PCU) respectively were studied by means of positron annihilation spectroscopy in the temperature range from 140 K to 360 K,DSC and WAXD measurements．The experimental results indicated that there were three structural transition temperatures for these two polyurethanes (PUs) from 140 K to 360 K．The transition at low temperature (at around 200 K) was attributed to the glass transition temperature (Tg) of polyester soft segments existing in PU and the transition at 275K could be related to the small amount water adsorbed in PU samples．The high temperature transition (at about 310 K) corresponded to the melting point of soft segment crystals in PBU and was also related to the Tg for compatible regions of the disordered hard segments with some soft segments existed in PCU．When the temperature was lower than the Tg of soft segments in PU,both the size and the relative concentration of free volume increased with increasing temperature for PBU and PCU．While the temperature was higher than the Tg of soft segmensts but lower than 275K,the relative concentration of free volume reached a constant value but the size of free volume increased further．When the temperature was higher than 275 K but lower than the melting point of soft segment crystals or the Tg of hard／soft segment miscible regions,the relative concentration of free volume still kept constant but the size of free volume increased appreciably．When the temperature increased more,both the size and the relative concentration of free volume existing in PUs increased again．The distributions of free volume were also examined at various temperatures for these two PUs．All these experimental results could be related to the movement of macromolecular chains and the morphologies for these PUs measured by using DSC and WAXD．
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发布时间：2021-03-19 - 摘要：A series of polyurethaneurea (PUU) aqueous dispersions were synthesized from castor oil and difunctional poly (oxypropylene) polyol(GE-210,Mn=1000),and the effect of castor oil／GE-210 composition on the morphologies and mechanical properties for these different PUU films was studied．The experimental results show that there was some compatibility between the hard segments and soft segments for the PUU based on GE一210,and the high degree of hydrogen-bonded urea carbonyl groups and the perfect ordered structure of hard segments observed for this kind of PUU resulted in higher tensile strength and elongation at break but lower elastic module and hardness of the film．For the PUU synthesized from castor oil,the degree of hydrogen-bonded urea carbonyl groups and the ordered structure of hard segments were suppressed by chemical crosslinking existing in the system,giving lower tensile strength and elongation at break but higher elastic module and hardness of the film．Furthermore,it is of interest to find that there were excellent comprehensive mechanical properties for the PUU films prepared with mixed polyols of castor oil and GE-210 in the composition range of around 50/50(wt/wt),which can be correlated with their structures and morphologies．
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发布时间：2021-03-19 - 摘要：Various substituted chitosan (PHCS) were prepared at 125℃ from chitosan and phthaloyl anhydride by controlling both the reaction time and molar ratio．The synthesis reaction mechanism and chemical structure of products were characterized by FTIR．Different compositions of amic acid-chitosan and imide-chitosan were found in these products．the former was converted into the latter at 125℃ after reacting relatively long time．The existence of amic acid-chitosan was proved by the good solubility and broad C—H stretch bands．as well as characteristic double bands of their salt (1455 and 1558 cm-1)．The existence of imide-chitosan was proved by characteristic double bands at 1712 and 1775 cm-1．The total degree of substitution(DSTotal) was determined with 1H-NMR．The degree 0f substitution for both amic acid (DS1) and imide(DS2) was measured by element analysis．The polarized optical microscopy was employed to study the texture and the critical concentration(c*) of liquid crystal phase in dichoroacetic acid．The c* (in polymer weight fraction) at which liquid crystalline ordering was found to be present was 0.12～0.18 for some PHCS,and too high (over the solubility of polymer)to be detected for PHCS with high relative degree of amic acid substitution．The c* was found to be affected mainly by the degree of substitution of amic acid．The c* increased directly with the increase of DS1．The influence of DS1 was significantly larger than that of DS2 on the critical liquid crystalline behavior of PHCS．
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发布时间：2021-03-19 - 摘要：The monomer reactivity ratios of emulsion copolymerization for some fluorine containing gaseous monomers,i．e．perfluoromethyl vinyl ether (PMVE) with TFE and PMVE with vinylidene fluoride (VDF) weremeasured and studied．At relatively low pressure,the copolymer composition equation could be kept in the same way as Mayo-Lewis equation after replacing the monomer concentration with gaseous mole fraction,and the monomer reactivity ratios with apparent monomer reactivity ratios．The initial and the end monomer mole fractions existing in the copolymerization systems were determined with gas chromatography (GC) and the copolymer compositions were calculated from the GC experimental data．The apparent monomer reactivity ratios estimated from reactivity ratio error-in variables model (RREVM) were γTFE=3.89,γPMVE=0.05 and γVDF=1.06,γPMVE=0.11 for these two copolymerization systems respectively．The composition of ternary copolymer composed of TFE／VDF／PMVE made from emulsion copolymerization was calculated according to the ternary copolymer composition equation with these apparent monomer reactivity ratios measured．It was found that the composition of such a ternary copolymer was in good agreement with that measured by means of 19F-NMR．
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发布时间：2021-03-19 - 摘要：Several aliphatic waterborne polyurethane prepolymers are prepared from isophorone diisocyanate,dimethylolpropanic acid,poly(butylene adipate) (PBA) and polypropylene glyco (PPG)．The prepolymers are blocked with 2-methoxyethanol,followed by neutralization pendant carboxyl by triethylamine,then diluted to 50 wt％ with methyl ethyl ketone,emulsified by adding deionized water under constant agitation．The principle of emulsification is explained．The aggregated structure of prepolymers in organic solvent is discussed．The prepolymer molecules with ionic groups can form segment microionic lattices．The emulsification process and phase inversion are characterized by using the variation of viscosity and conductivity．The emulsification process includes the dissociation of the segment microionic lattices and the aggregation of the hydrophobic segments．The inversion process can be clearly divided into three regions depending upon the variation of viscosity and conductivity．The experimental results show that several factors can affect the phase inversion heavily,including the molecular weight and type of soft segments,the[NCO]／[OH] ratio,carboxyl content and neutralization degree．With the increasing of the molecular weight of soft segment,the phase inversion delays．In addition,the phase inversion of PBA-based prepolymer occurs earlier than that of PPG-based prepolymer,while their soft-segment molecular weights are equal．High[NCO]／[OH] ratio not only decreases the viscosity of both prepolymer solution and emulsification system,but also makes phase inversion occur earlier．With the increasing of carboxyl content,the phase inversion occurs early．In the meantime appropriate carboxyl content can decrease the viscosity of phase inversion point and lead to easy phase inversion．The decrease of neutralization degree can contribute to low viscosity and early phase inversion．Selecting appropriate conditions can optimize the emulsification process．
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发布时间：2021-03-19 - 摘要：A novel elastomeric polyurethane／clay (PU／Clay) nanocomposite based on poly(propylene glycol),glycerol propoxylate and toluene-diisocyanate were synthesized by intercalative polymerization technology．The results of X-ray diffraction study showed that the gallery distance of the clay was enlarged from l.9nm to 4.5 nm or more．Introducing about 7.5 wt％ clay in the composites resulted in／more than two-fold increase in the tensile strength and five-fold increase in the elongation at break as compared to those of the pure PU．Additionally,the thermal stability of the PU/Clay nanocomposites was also studied by TGA analysis．The thermal stability of the nanocomposites was increased sightly in comparing with the pure PU．
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发布时间：2021-03-19 - 摘要：A new IPN hydrogel poly(N-vinyl pyrrolidone-co-β-hydropropyl acrylate)／poly(acrylic acid) was synthesized．and its temperature and pH sensitive behavior was studied．In acidic medium the swelling ratio (SR) of this hydrogel slumps suddenly and drops quickly with temperature rising due to the hydrogen bond formation between PNVP and PAA．In alkaline medium,the SR of the IPN hydrogel rises as the temperature is raised．
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发布时间：2021-03-19 - 摘要：High trans-polybutadiene (over 96％ trans 1,4-content) was prepared by lanthanum naphthenate,dibutyl magnesium and THF catalytic system．The dependence of polymerization on molar ratio of catalyst components (Mg／La,Mg／THF),different rare earth elements．solvents and temperature was studied in detail．It was found that the dependence of polymerization rate on monomer concentration followed the 1st order relationship．
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发布时间：2021-03-19 - 摘要：Functional monomers,maleic anhydride (MAH) and vinyl acetate (VAc) were used as co-monomers in the solid grafting process of polypropylene (PP) The high graft ratio of both VAc and MAH were obtained when the initial mole ratio of MAH/VAC approaches l:1．The reaction mechanism was that molecules of these two monomers could form a stable transition state during the graft polymerization process,and then the reaction activity of both molecules was enhanced．At the same time,the product’s melt flow rate (MFR) was decreased with the increase of VAc’s dosage．This multifunctional PP containing anhydride groups and ester groups at the same time can widen PP’S application area and will promote the realization of novel PP blends．
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发布时间：2021-03-19 - 摘要：Synthesis 0f half-metallocene complexes ([O,O]CpTiCl) containing bisphenoxy ligands is discribed,while their composition and structure are characterized by elemental analysis,IR and 1H-NMR,suggesting that the ring structure is formed by the combination of the two oxygen atoms in the biphenol ligand [O,O] and the titanium atom．It is proved by the experiments that [O,O] CpTiCl is active for ethylene polymerization at 30℃ and latm with MAO activation,and exibits much higher activity that CpTiCl3,and the results show that the activity decreases successively with increase in the aromatic ings(C6H4O2)>(C12H8O2)>(C20H12O2)．For the(C6H4O2)CpTiCl/MAO system,the activity is a“up and down” type with increase in the Al／Ti molar ratio,and up to the highest value around 1×105 gPE／molTi·h when the Al/Ti molar ratio is 500 to 3000．The polyethylene obtained is characteristic of bi-model distribution with an average molecular weight Mw=12.5×104 and molecular weight distribution Mw/Mn=7.4
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发布时间：2021-03-19 - 摘要：Macromonomer poly(N-vinylformamide) and functional polymer microspheres are synthesized by radical polymerization,respectively．The properties of the macromonomer and the functional polymer microspheres have been studied by GPC．spectrophotometer and SEM．The results indicate that the macromonomer and the microspheres possess definite properties of thermo-sensitivity．Moreover the functional polymer microspheres have monodispersibity and its particle diameter is in the range of l～5μm．
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发布时间：2021-03-19 - 摘要：Porous polyurethane (PU) membranes were prepared via thermally induced phase separation (TIPS) technique by employing a home—made mould consisting of a solution container,a membrane-forming platform,acoldplate,a temperature-decreasing system and a temperature-supervising system．The influences of polymer concentration on the surface morphology,pore size,porosity and water vapor transmitting ratio of the porous PU membranes were studied．The bottom surfaces,the surfaces contacting with the membrane-forming platform,of the porous PU membranes are planar and smooth for all the selected polymer concentrations,e．g．φ2 from 0.025 to 0.078．The pore sizes ale smaller and are estimated in the range of nanometer．While the top surfaces,the free surfaces toward air,possess variable surface morphology and have micrometer-sized pores that are larger than those of the bottom surfaces．This phenomenon is mainly caused by the different oarsening time after spinodal phase separation (polyurethane/l,4-dioxane (DO) solution is an upper critical temperature phase separation system)． Preliminary studies showed that the pore sizes and surface morphology of porous PU membranes were also influenced by the temperature of the coldplate and by the composition of solvents,DO／H2O,a good solvent and a poor solvent for the PU,respectively．
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发布时间：2021-03-19 - 摘要：The living cationic polymerization of β-pinene was carried out with α-chloroethylbenzene／Ti(OiPr)4／TiCl4(Ti(OiPr)4/TiCl4 mole ratio：1／3) initiating system in CH2C12 at -40℃．After 25 min of reaction(β pineneconversion～100％),the resulted living poly(β-pinene) was capped with a few units of styrene and then the polymerization Was quenched to giveβ-pinene macroinitiator with banzyl chloride chain end (P(β-p)-St-Cl)．1H-NMR analysis of the obtained polymer showed that each macroinitiator molecule possessed almost one banzyl chloride end group．The macroinitiator in conjunction with Ti(OiPr)4／TiCl4(Ti(OiPr)4/TiCl4 mole ratio：1/3) could readily initiate the cationic polymerization of styrene to give β-pinene／styren block copolymers．The macroinitiator was also used to initiate the atom transfer radical polymerization of methyl methacrylate (MMA) in the presence of CuCl/2,2'-bipyridine．The product was a mixture ofβ-pinene／MMA block copolymer and unreacted macroinitiator,indicating that the initiating efficiency was below 100％．
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发布时间：2021-03-19 - 摘要：A novel monomer the 1-methyl-4,5-bis (4-chlorobenzoy) cyclometer containing cyclohexene were prepared,so a group of novel poly(aryl ether)s containing the cyclohexene and phthalazinone moieties was prepared by the nucleophilic displacement reaction of 1-methy l-4,5-bis(4-chlorobenzoyl) cyclohexene and 4,4’-dichlorodiphenyl sulfone and 4-(3,5-dimethyl-4-hydroxyphenyl)-2,3-phthalazin-1-one．The polymer was studied by FT-IR,1H-NMR,DSC,X-ray diffraction．It has been proved that it was an amorphous plastics with high glass temperature,soluble in some solvents at room temperature and the polymer was also an intermediate product of cross-linked copolymer and grafted copolymer．It can supply with a good basis for getting poly(aryl ether)s crosslinked,grafted and other special polymers with various structures and function by changing crosslinked density and grafted density through binary copolymerization or trimerization．
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发布时间：2021-03-19 - 摘要：A new type hydrophilic monomer (K600) with both ionic groups and nonionic segments is synthesized from polyethylene oxide (Mn=600) and 1,2,4,5-benzenetetracarboxylic dianhydride (BTDA)．The synthesis process is monitored with FT-IR．Several selfemulsifiable polyurethane emulsions are prepared from isophorone diisocyanate(IPDI),poly(butylene adipate)(PBA) and K600 in a prepolymer mixing process using substantial amount of solvent．The acid groups are neutralized with triethylamine (TEA)．The emulsion based on dimethylolpropanic acid (DMPA) is prepared by the same procedure for comparison．The effect of K600 content on the characteristics of emulsions,such as visual appearance,particle size,viscosity,durability to frost,electrolytes and variation of pH．are studied．Since K600 has been neutralized with TEA to give an anionic species,which is hydrophilic in nature,the hydrophilicity of polymer chains increases with increasing the K600 content．As a result,the particle size becomes finer(<100 nm) while the emulsion appearance varies from white to translucent and the viscosity of emulsion increases accordingly．In the meantime,the ionic groups and nonionic segments have a synergistic effect．The emulsion with over 1.7 wt％ carboxyl content can endure high temperature (80℃) for more than 120 h and the variation of emulsion viscosity is very low after frost．The emulsion with over 1.0 wt％ carboxyl content is stable within a pH range from l to 14 and can be mixed with l0％ NaCl solution at any ratio without any sedimentation．On the other hand．the emulsion based on DMPA is very sensitive to the variation of pH values and electrolytes．In conclusion,K600 can provide the emulsions excellent stability．
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发布时间：2021-03-19 - 摘要：The membrane of cobalt electropolyurushiol coordination polymer was obtained by the reaction of cobalt chloride isopropyl alcohol solution with electropolyurushiol．The membrane of coordination polymer was characterized by FT-IR,XPS,DTA-TG,DMTA and AES,and its composition and structure were determined．Each Co2+ ion was coordinated with hydroxyls of two units in the EPU molecule,and cross-link was formed further because of producing σ coordination bond,thus hydrophobic membrane of coordination polymer was formed．Therefore its glass transition temperature increased and heat resistance was enhanced considerably．It was found that the coordination polymer membrane activated by Na2SO3 can catalyze polymerization of VAc in water phase in room temperature．
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发布时间：2021-03-19 - 摘要：By means of the normal random walk (NRW) and self-avoiding walk (SAW) as the models of a polymer chain,the conformational properties of a polymer chain near an impenetrable plane were investigated,which gave the conformational entropy and chain size as functions of z0,the distance of one chain end to the plane．The computer simulation techniques used include the exact enumeration and Monte Carlo simulation．It was shown that the decrease in the conformational entropy of this confined polymer chain obeys a simple law．The reduction of achain in conformational entropy due to the confining effect of a surface increased with increasing the chain length and decreasing the distance z0．The mean square end-to-end distance (especially its z-component) of the confined polymer chain near an impenetrable plane was larger than the corresponding value of the free chain,as the end distance z0 was very small．When the end distance z0 increased the ratio of 〈R2〉 and〈R2z〉 decreased in the beginning,reached a minimum and then increased at last．As the end distance z0→∞,this ratio approached to alimit value equal to the corresponding value of a free chain．In other words,the size of the polymer chain wasexperienced a process of rapid contraction and then gradual extension．
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发布时间：2021-03-19
Research Article
- 摘要：The effects of CaCO3 on the crystallization behavior of polypropylene (PP) were studied by means of DSC and WAXD．The average sizes of the CaCO3 powders used were 0.1 μm (UC) and 0.5μm (Gc),respectively．The PP／CaCO3 composites at compositions of 1 phr and 10 phr were investigated．The results showed that the addition of CaCO3 reduced the supercooling,the rate of nucleation and the overall rate of crystallization (except for the 10 phr UC/PP sample)．The crystallinity of PP was increased and the size distribution of the crystallites of α-PP was broadened．On the other hand,the crystallization rate of 10 phr UC／PP is 1.5 times higher than that of neat PP．It has an overall rate of crystallization 2 times as much as that of the neat PP and has the maximum crystallinity．The sizes of crystallites and the unit cell parameters of α-PP were varied by the addition of CaCO3．β-PP was formed by addition of GC and was not detected by addition of UC．The differences of crystallization behaviors of PP might be attributed to the combined effects of the content and size of CaCO3 filled．
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发布时间：2021-03-19 - 摘要：Electruluminescence (EL) in conjugated polymers based on phenyleneethynylene and thiophene (PPE) with C—C triple bonds in their main chains were studied．It was found that the emitting wavelength will red-shift by introduction of thiophene which is an electron-rich moiety,the results suggest that electron-rich moieties should increase effective conjugation length．Our results also show that the incorporation of thiophene units into PPE may significantly reduce the rigid-rod conformation and improve the processibility．
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发布时间：2021-03-19 - 摘要：An acrylic monomer bearing carbazole-moiety,3-methacrylamido-9-ethylcarbazole (MAECz) was synthesized and polymerized radically．Fluorescence studies showed that at the same chromophore concentration,the fluorescence intensity of the polymer (P(MAECz) was much stronger than that of the monomer．This can be explained by what we termed fluorescence“Structural Self-Quenching Effect”(SSQE). The stem—volmer constants of P(MAECz) in solution quenched by several electron deficient vinyl monomers were obtained．It was found that the quenching efficiency of the quenchers was relevant to the degree of the electron deficiency. Also,the photopolymerization of acrylonitrile (AN) initiated by MAECz was investigated kinetically and a tentative initiation mechanism was proposed．
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发布时间：2021-03-19 -
PREPARATION OF MONODISPERSE POLYSTYRENE MICROSPHERES BY SHELL POROUS GLASS-SUSPENSION POLYMERIZATION
摘要：Monodisperse polystyrene microspheres are prepared by shell porous glass (SPG)-suspension polymerization．The influences of SPG on size and size dispersity of the microspheres are investigated．The properties of the microspheres are studied by GPC,TEM and SEM．The results indicate that the polystyrene microspheres possess definite monodispersibity and their particle size is in the range of 5～12 μm．- 6
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发布时间：2021-03-19 - 摘要：Enantioselective alternating copolymerization of carbon monoxide with 1-heptene was carried out using palladium catalyst modified hy 1,4-3,6-dianhydro-2,5一dideoxy-2,5-bis(diphenylphosphino)-L-iditol (DDPPI)．The chiral diphosphine was proved to be effective at enantioselective copolymerization．The pure poly(1,4-ketone) was obtained by dissolving the copolymer containing spiroketal and 1,4-ketone units in 1,1,1,3,3,3-hexafluoro-2-propanol and reprecipitating with methanol．Optical rotation,elemental analysis,spectra of 1H-NMR,13C-NMR and IR showed that our copolymer was optically active,isotatic,alternating poly(1,4-ketone) structure．The copolymerization was carried out at 45℃ for 48 h．Molecular weight：Mn=4.02×103,Mw／Mn=1.55 (GPC measurements with polystyrene standards)．Optical rotation：[α]20589=+63。 (CH2Cl2,5.0 mg／mL)．Tm=194℃,Tg=11℃．
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发布时间：2021-03-19 - 摘要：A new copoly(ether ketone ketone)(NPEKK)has been synthesized from 4,5-bis(4-fluorobenzoyl)-l-methylcyclohexene,4-(4-hydroxyphenyl)-2,3-phthalazin-l-one and 2,2-p-hydroxyphenyl一iso-propane via nucleo-philic polycondensation reaction．The ring-closing reaction of NPEKK with hydrazine gives the cyclizing product CNPEKK．The new polymers have been studied with FT-IR．DSC and TGA．It has been proved that the synthesized poly(ether ketone ketone)s is very soluble in many organic solvents,thermal stable and have good tensile properties．While,CNPEKK is more stable,but less soluble．
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发布时间：2021-03-19 - 摘要：The hydrogen-bond defect of water in PVA hydrogels was studied by Raman spectral analysis．The PVA hydrogels were prepared from PVA of different DP in different concentrations via freeze／thawed method．It was found that the hydrogen bond defect of water in PVA hydrogels is affected by their crystallinity which was depended on the molecular weight and concentration of PVA and also the number of freeze／thawed cycles．After swelling in water for 24 h,partial VA units were released from the crystalline regions,this means that more‘free’VA units could bond with water in PVA hydrogels,causing the decrease of C value and the increase of N value．
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发布时间：2021-03-19 - 摘要：Phase separation behavior of the water-soluble binary anionic acrylamide copolymer series (P3A) composed of non-ionic monomer acrylamide (AM),weak acidic monomer acrylic acid (AA) and strong acidicmonomer 2-acrylamido-2-methylpropanesulfonate (AMPS) was studied in the Ca2+ ion aqueous solution．The P3A was found to exhibit an unusual phase separation behavior,which relates with structure and composition of the polymer,as well as the concentration and temperature in the dilute P3A solution．A non-linear relationship appeared between the critical temperature Tc of phase separation and the metal salt concentration with a minimum at the mid-position,whereas the Tc remains constant as varying polymer oncentration．From comparison of the effects of AA and AMPS units on the phase separation behavior of P3A polymers the results obtained indicate that excent for the difference in acidity of two anionic units,the phase separation is mostly affected by the structure of anion unites in the polymer chain．The AMPS units exhibit a good stability under the action of Ca2+ ions due to their great steric influence of side chains compared to AA units．Therefore,containing more AMPS,the polymer (P3A) becomes the more resistant to phase separation in the divalent metal salt solution．
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发布时间：2021-03-19 - 摘要：Reverse addition-fragmentation chain transfer (RAFT) polymerizatin of MAn with St is reported aiming at the synthesis of a well-defined alternating copolymer of MAn with St．The results show that the polymers possess predetermined molecular weight and molecular weight distribution as narrow as 1.2．A novel well-defined block copolymer P(MAn-alt-St)-b—PSt has also been prepared by the copolymerization of MAn with excess amount of St in molar feed via RAFT process．
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发布时间：2021-03-19 - 摘要：Controlled radical copolymerization including atom transfer radical polymerization(ATRP) and radical reversible addition-fragmentation chain transfer polymerization(RAFT) of iso-butyl vinyl ether (iBVE) with electron-withdrawing monomers such as maleic anhydride and N-substituted maleimides,have been studied．Results show that ATRP of iBVE with electron-withdrawing monomers does not work well,while the well-defined copolymers are obtained via RAFT polymerization．The copolymers thus obtained possess alternating structure,predetermined molecular weight and molecular weight distribution as narrow as 1.2～1.4．
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发布时间：2021-03-19 - 摘要：Two catalyst precursors—DPB (N,N′-diphenyl-2,3-butadiimine) and PDP (N-phenyl-2,5-dimethyl-pyrrole) were synthesized by reactions of diketones and aniline in alcohol．N,N′-diphenyl-2,3-butadiimine and N-phenyl-2,5-dimethyl-pyrrole were characterized by IR,1H-NMR and MS,and were found to have diimine and substituted pyrrole ring structure,respectively．The condensates N,N′-diphenyl-2,3-butadiimine and N-phenyl-2, 5-dimethyl—pyrrole both were treated with ZnEt2 and then with methnol,resulting in Zn complexes with the diketone-aniline condensates (DPBZn and PDPZn)．The two complexes were applied as catalysts for the copolymerization of CO2 and cyclohexene oxide．One mole of DPBZn and DPDZn may generate 3000 and 16800 g of polymers,respectively．The obtained copolymers were also determined to have CO2 fractions of 0.424-0.476 (by 1H-NMR)and instrinsic viscosity [η] of 0.115～0.368 dL／g in chloroform at 30℃．
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发布时间：2021-03-19
Research Bulletin
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