Silk was grafted using 2-hydroxyethyl methacrylate(HEMA)by atom transfer radical polymerization(ATRP)method.The amino groups and hydroxyl groups on the side chains of the silk fibroin was reacted with 2-bromoisobutyry...Silk was grafted using 2-hydroxyethyl methacrylate(HEMA)by atom transfer radical polymerization(ATRP)method.The amino groups and hydroxyl groups on the side chains of the silk fibroin was reacted with 2-bromoisobutyryl bromide(BriB-Br)to obtain efficient macroinitiator for ATRP.And the macroinitiator was grafted with HEMA in water aqueous using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)as catalyst system.The effects of monomer concentration,the proportion of CuBr and PMDETA,grafting temperature and time on the silk grafting were discussed,and the optimal grafting technology was obtained.FT-IR characterization of the grafted silk showed a peak corresponding to HEMA,which indicated that HEMA was grafted onto the surface of silk.ATRP method could be applied on the silk modification and this technique provided a new way for silk grafting.展开更多
A series of homo and copolymers of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, tetrahydrofuran, and benzene) have been investigated by free radical polymerization method. The sa...A series of homo and copolymers of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, tetrahydrofuran, and benzene) have been investigated by free radical polymerization method. The samples obtained from the synthesis were characterized by Fourier Transform-Infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (<sup>1</sup>H NMR), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The results show that the synthesis of the polymers is more feasible under neat conditions rather than solvent directed reaction. Moreover, the DSC data shows that the polystyrene obtained is amorphous in nature and therefore displayed only a glass transition signal rather than crystallization and melting peaks. In addition, this study indicates that homolopolymerization of styrene via free radical polymerization tends to be preferable in less polar solvents like THF than in non-polar solvents like benzene. Benzene might destabilize the formation of the reactive radicals leading to the formation of the products. In summary, the homolpolymerization of styrene is more feasible than the homopolymerization 2-hydroxyethyl methacrylate under the experimental setup used. Styrene is more reactive than 2-hydroxyethyl methacrylate than free radical polymerization reaction due in part of the generation of the benzylic radical intermediate which is more stable leading to the formation of products than alkyl radical which are less stable. Furthermore, polymerization of styrene under neat conditions is preferable in solvent-assisted environments. The choice of solvent for the synthesis of these polymers is crucial and therefore the selection of solvent that leads to the formation of a more stable reaction intermediate is more favorable. It is worth noting that the structure of the proposed copolymer consists of a highly polar and hydrophilic monomer, 2-hydroxyethyl methacrylate and a highly non-polar and hydrophobic monomer, styrene. These functionalities constitute an amphiphilic copolymer with diverse characteristics. A plausible explanation underlying our observations is that the reaction conditions employed in the synthesis of these copolymers might not be the right route required under free radical polymerization.展开更多
Multiarm star block copolymers hyperbranched polyethylenimine-b-poly(2-hydroxyethyl methacrylate) (HPEI-b- PHEMA) with average 28 PHEMA arms have been prepared by atom transfer radical polymerization (ATRP) of H...Multiarm star block copolymers hyperbranched polyethylenimine-b-poly(2-hydroxyethyl methacrylate) (HPEI-b- PHEMA) with average 28 PHEMA arms have been prepared by atom transfer radical polymerization (ATRP) of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuC1 and the molar ratio of [CuCl]:[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln([M]0/[M]t) on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic guests, but the amidated HPEI core was more effective than the PHEMA shell.展开更多
The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polyme...The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polymerization and the overall activation energy of polymerization were determined. Based on kinetics study and the end group analysis of the polymer obtained by UV spectrum method, the initiation mechanism is proposed.展开更多
Comblike poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical p...Comblike poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical polymerization of ethyl 2-bromoacrylate. The obtained comblike polymers were characterized by GPC and 1H NMR.展开更多
Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone ce...Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone cement are limited by the high elasticity modulus of PMMA,its low biodegradability,and its limited ability to regenerate bone.To improve PMMA bio activity and biodegradability and to modify its elasticity modulus,we mixed PMMA bone cement with oxidized hyaluronic acid and carboxymethyl chitosan in situ cross-linking hydrogel loaded with bone morphogenetic protein-2(BMP-2)to achieve novel hybrid cement.These fabric ated PMMA-hydrogel hybrid cements exhibited lower setting temperatures,a lower elasticity modulus,and better biodegradability and biocompatibility than that of pure PMMA cement,while retaining acceptable setting times,mechanical strength,and inj ectability.In addition,we detected release of BMP-2 from the PMMA-hydrogel hybrid cements,significantly enhancing in vitro osteogenesis of bone marrow mesenchymal stem cells by up-regulating the gene expression of Runx2,Coll,and OPN.Use of PMMA-hydrogel hybrid cements loaded with BMP-2 on rabbit femoral condyle bone-defect models revealed their biodegradability and enhanced bone formation.Our study demonstrated the favorable mechanical properties,biocompatibility,and biodegradability of fabricated PMMA-hydrogel hybrid cements loaded with BMP-2,as well as their ability to improve osteogenesis,making them a promising material for use in PKP and PVP.展开更多
A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism,which included the atom...A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism,which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0×10^4L·mol^-1·s^-1 and 0.04L·mol^-1·s^-1, respectively. The rate constant of the propagation of growing polymer radical is 8.50L·mol^-1·s^-1, and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radical are 0.045L·mol^-1·s^-1 and 1.2×10^5L·mol^-1·s^-1, respectively. The values of the rate constants represent the features of the ATRP process. The kinetic model was used to calculate the ATRP process of DMAEMA. The results show that the calculations agree well with the measurements.展开更多
The 2,2-dinitropropyl methacrylate(DNPMA) was synthesized by esterification of α-methacrylic acid with 2,2-dinitropropanol.The free-radical bulk polymerization of DNPMA in the presence of 2,2-azobisisobutyronitrile...The 2,2-dinitropropyl methacrylate(DNPMA) was synthesized by esterification of α-methacrylic acid with 2,2-dinitropropanol.The free-radical bulk polymerization of DNPMA in the presence of 2,2-azobisisobutyronitrile(AIBN) was investigated by differential scanning calorimetry(DSC) in the nonisothermal mode.Kissinger,Ozawa and Barrett methods were applied to determine the activation energy(Ea) and the reaction order of the free-radical polymerization.The results showed that the temperature of exothermic polymerization peaks increased with increasing heating rate.With increasing the molar ratio of monomer/initiator and the heating rate,the reaction order of nonisothermal polymerization was approximately equal to 1.The average Ea value from Kissinger and Ozawa methods(77.74±1.07 kJ/mol) was smaller than the value from the Barrett method(Ea=102.36 kJ/mol).展开更多
A novel methacrylate monomer with bulky side group, tri(2-pyridyl)methyl methacrylate (Tr2PyMA), was synthesized and polymerized. The polymer obtained by radical polymerization exhibits high isotactic tacticity.
A new kind of polymethyl methacrylate (PMMA)-TiO2 nanocomposite was synthesized through polymerization. The thermal and photic stability of this PMMA TiO2 nanocomposites were investigated. The as prepared samples we...A new kind of polymethyl methacrylate (PMMA)-TiO2 nanocomposite was synthesized through polymerization. The thermal and photic stability of this PMMA TiO2 nanocomposites were investigated. The as prepared samples were characterized by scanning electron microscopy (SEM), UV-Vis spectroscopy, differential thermal analysis (DTA) and the photo-induced weight loss, The results show that the photostability of the PMMA-TiO2 nanocomposite is higher than that of the pure PMMA under UV-light irradiation, The weight loss of the pure PMMA reaches 30 % after 300 h UVirradiation, while the composite only 0.3% under the identical experimental condition. The glass transition temperature (TR) of pure PMMA is only 80℃, while the Tg of the composite reaches 258℃. Compared with pure PMMA, the thermal stability of the composite is greatly enhanced.展开更多
Silicone rubber films were modified by the consecutive grafting of 2-(diethylamino)ethyl methacrylate (DEAEMA) and N-vinylcaprolactam (NVCL) using direct method on two steps with gamma-rays. The effect of absorbed dos...Silicone rubber films were modified by the consecutive grafting of 2-(diethylamino)ethyl methacrylate (DEAEMA) and N-vinylcaprolactam (NVCL) using direct method on two steps with gamma-rays. The effect of absorbed dose and monomer concentration on grafting degree was determined. The grafted samples were verified by FTIR-ATR spectroscopy and swelling;thermal properties were analyzed by DSC and TGA. The stimuli-responsive behavior was studied by swelling and/or DSC. Thermo- and pH-sensitive films of (PP-g-DEAEMA)-g-NVCL presented a pH critical at 3.2 and LCST around 63.5℃.展开更多
An efficient protocol for the synthesis of N^6-(2-Hydroxyethyl)adenosine and its analogues through nucleophilic substitution was developed. All the reactions were completed in 10 rain under microwave irradiation. Us...An efficient protocol for the synthesis of N^6-(2-Hydroxyethyl)adenosine and its analogues through nucleophilic substitution was developed. All the reactions were completed in 10 rain under microwave irradiation. Using water as solvent makes our method eco-friendly and easy to handle with.展开更多
Studies on the degradation process of waste polyethylene terephthalate(PET)have become increasingly mature,but there are relatively few studies on the separation of degradation products.The products contain many compo...Studies on the degradation process of waste polyethylene terephthalate(PET)have become increasingly mature,but there are relatively few studies on the separation of degradation products.The products contain many components and the separation of which is difficult.Therefore,the study on phase equilibrium thermodynamics of bis-2-hydroxyethyl terephthalate(BHET)is of great theoretical significance and practical value to provide basic data for the BHET crystallization separation.In this work,the degraded products were purified and characterized.The solubility of BHET in methanol,ethanol,ethylene glycol,water and the mixture of ethylene glycol+water were determined by static method.The experimental results were correlated with different models,such as ideal solution(IS)model,λh equation,Apelblat equation and NRTL model.Based on the van’t Hoff equation,the mixing Gibbs energy,enthalpy and entropy were calculated.From this work,the basic data which can be used to guide the crystallization process of BHET were obtained,including solubility data,correlation model and thermodynamic properties.展开更多
The copolymerization of 2-hydroxyethyl acrylate (HEA, M//1) and methyl methacrylate (MMA, M//2) in cyclohexanone was studied. The multiple experiments of solution copolymerization with low conversion were carried out...The copolymerization of 2-hydroxyethyl acrylate (HEA, M//1) and methyl methacrylate (MMA, M//2) in cyclohexanone was studied. The multiple experiments of solution copolymerization with low conversion were carried out at two sensitive composition feed points at 60, 80, 100, 120 and 140 degree C, respectively. The composition of the copolymers was analyzed by **1H-NMR. The reactivity ratios which were estimated by the Error-in-Variable Method (EVM) of Mayo-Lewis equation were found to be r//1 equals 0.328, r//2 equals 1.781 for 60 degree C; 0.375, 1.709 for 80 degree C; 0.406, 1.654 for 100 degree C; 0.439, 1.540 for 120 degree C and 0.455, 1.400 for 140 degree C, and the 95% joint confidence intervals of the reactivity ratios were also determined. According to r//1 and r//2, Arrhenius relations and the activity energy difference between the homo- and cross-propagation were calculated. (Author abstract) 12 Refs.展开更多
Polyfluoroalkyl substituted 2-hydroxyethyl acrylate 6 was synthesized in six steps usingglycerol as a starting material. A preliminary investigation has been taken on the synthesisand characterization of copolymers of...Polyfluoroalkyl substituted 2-hydroxyethyl acrylate 6 was synthesized in six steps usingglycerol as a starting material. A preliminary investigation has been taken on the synthesisand characterization of copolymers of 6 and 2-hydroxyethyl methacrylate.展开更多
Optically active copolymers of pairs of three monomers, triphenyl (methyl methacrylate)and one or two pyridyl substituted methyl methacrylate homologues, were obtained by helix-sense-selective copolymerization using c...Optically active copolymers of pairs of three monomers, triphenyl (methyl methacrylate)and one or two pyridyl substituted methyl methacrylate homologues, were obtained by helix-sense-selective copolymerization using complexes of organolithium with chiral ligand as anionicinitiators in toluene at low temperature. The copolymers obtained with (-)-sparteine (Sp) and(S,S)-(+)-and (R, R)-(-)-2, 3-dimethoxy-1, 4-bis (dimethylamino) butanes((+)-and (-)-DDB) complexes of organolithium showed low optical activity, but PMP complex with N, N-diphenylethyleneamine monolithium amide (PMP-DPEDA-Li) was effective in synthesizingcopolymers of high optical rotation ([α]_D^(25) about+320~1370°)which were comparable to thoseof relative homopolymers with one-handed helical structure.展开更多
Lithium aluminium amide [LiAI(NHR)4] 5 obtained by treating the primary amine 4 with LiAlH4 could promote the ring opening of epoxide 2 and led to high regioselective product of racemic bis[2-(6-fluoro-2-chromanyl...Lithium aluminium amide [LiAI(NHR)4] 5 obtained by treating the primary amine 4 with LiAlH4 could promote the ring opening of epoxide 2 and led to high regioselective product of racemic bis[2-(6-fluoro-2-chromanyl)-2-hydroxyethyl]amine methanesulfonic acid salt 7.展开更多
基金National Natural Science Foundation of China(No.50673071,No.50973079)Natural Science Fund for Colleges and Universities in Jiangsu Province,China(No.07KJD540188,No.09KJA540001)
文摘Silk was grafted using 2-hydroxyethyl methacrylate(HEMA)by atom transfer radical polymerization(ATRP)method.The amino groups and hydroxyl groups on the side chains of the silk fibroin was reacted with 2-bromoisobutyryl bromide(BriB-Br)to obtain efficient macroinitiator for ATRP.And the macroinitiator was grafted with HEMA in water aqueous using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine(PMDETA)as catalyst system.The effects of monomer concentration,the proportion of CuBr and PMDETA,grafting temperature and time on the silk grafting were discussed,and the optimal grafting technology was obtained.FT-IR characterization of the grafted silk showed a peak corresponding to HEMA,which indicated that HEMA was grafted onto the surface of silk.ATRP method could be applied on the silk modification and this technique provided a new way for silk grafting.
文摘A series of homo and copolymers of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, tetrahydrofuran, and benzene) have been investigated by free radical polymerization method. The samples obtained from the synthesis were characterized by Fourier Transform-Infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (<sup>1</sup>H NMR), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The results show that the synthesis of the polymers is more feasible under neat conditions rather than solvent directed reaction. Moreover, the DSC data shows that the polystyrene obtained is amorphous in nature and therefore displayed only a glass transition signal rather than crystallization and melting peaks. In addition, this study indicates that homolopolymerization of styrene via free radical polymerization tends to be preferable in less polar solvents like THF than in non-polar solvents like benzene. Benzene might destabilize the formation of the reactive radicals leading to the formation of the products. In summary, the homolpolymerization of styrene is more feasible than the homopolymerization 2-hydroxyethyl methacrylate under the experimental setup used. Styrene is more reactive than 2-hydroxyethyl methacrylate than free radical polymerization reaction due in part of the generation of the benzylic radical intermediate which is more stable leading to the formation of products than alkyl radical which are less stable. Furthermore, polymerization of styrene under neat conditions is preferable in solvent-assisted environments. The choice of solvent for the synthesis of these polymers is crucial and therefore the selection of solvent that leads to the formation of a more stable reaction intermediate is more favorable. It is worth noting that the structure of the proposed copolymer consists of a highly polar and hydrophilic monomer, 2-hydroxyethyl methacrylate and a highly non-polar and hydrophobic monomer, styrene. These functionalities constitute an amphiphilic copolymer with diverse characteristics. A plausible explanation underlying our observations is that the reaction conditions employed in the synthesis of these copolymers might not be the right route required under free radical polymerization.
基金financially supported by the Program for New Century Excellent Talents in Universitiesthe National Natural Science Foundation of China (Nos. 21074088, 31201426)
文摘Multiarm star block copolymers hyperbranched polyethylenimine-b-poly(2-hydroxyethyl methacrylate) (HPEI-b- PHEMA) with average 28 PHEMA arms have been prepared by atom transfer radical polymerization (ATRP) of HEMA in a mixed solvent of methanol and water using a core-first strategy. The hyperbranched macroinitiator employed was prepared on the basis of well-defined hyperbranched polyethylenimine with Mw/Mn of 1.04 by amidation with 2-bromo-isobutyryl bromide. The polymerization condition was optimized to prepare star copolymers with narrow dispersity, and the variables included the volume ratio of methanol to water, the molar ratio of initiating site to CuC1 and the molar ratio of [CuCl]:[CuBr2]. Under the optimized polymerization condition, the lowest Mw/Mn value of the obtained star copolymers was around 1.3. Kinetic analysis showed that an induction period existed in the polymerization of HEMA. After this induction period, a linear dependence of ln([M]0/[M]t) on time was observed. The obtained HPEI-b-PHEMA could adsorb hydrophilic molecules. The comparison with the star copolymer with hydrophobic core and hydrophilic PHEMA shell verified that both the hydrophilic core and shell could host the hydrophilic guests, but the amidated HPEI core was more effective than the PHEMA shell.
基金The project supported by the National Natural Science Foundation of China
文摘The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polymerization and the overall activation energy of polymerization were determined. Based on kinetics study and the end group analysis of the polymer obtained by UV spectrum method, the initiation mechanism is proposed.
文摘Comblike poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical polymerization of ethyl 2-bromoacrylate. The obtained comblike polymers were characterized by GPC and 1H NMR.
基金supported by the National Key R&D Program of China(No.2018YFA0703000)the National Natural Science Foundation of China(Nos.82071564,82072412,and 81772326)+1 种基金the Fundamental Research Program Funding of Ninth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine(No.JYZZ070)Project of Shanghai Science and Technology Commission(No.19XD1434200/18431903700)。
文摘Poly methyl methacrylate(PMMA)bone cement is used in augmenting and stabilizing fractured vertebral bodies through percutaneous vertebroplasty(PVP)and percutaneous kyphoplasty(PKP).However,applications of PMMA bone cement are limited by the high elasticity modulus of PMMA,its low biodegradability,and its limited ability to regenerate bone.To improve PMMA bio activity and biodegradability and to modify its elasticity modulus,we mixed PMMA bone cement with oxidized hyaluronic acid and carboxymethyl chitosan in situ cross-linking hydrogel loaded with bone morphogenetic protein-2(BMP-2)to achieve novel hybrid cement.These fabric ated PMMA-hydrogel hybrid cements exhibited lower setting temperatures,a lower elasticity modulus,and better biodegradability and biocompatibility than that of pure PMMA cement,while retaining acceptable setting times,mechanical strength,and inj ectability.In addition,we detected release of BMP-2 from the PMMA-hydrogel hybrid cements,significantly enhancing in vitro osteogenesis of bone marrow mesenchymal stem cells by up-regulating the gene expression of Runx2,Coll,and OPN.Use of PMMA-hydrogel hybrid cements loaded with BMP-2 on rabbit femoral condyle bone-defect models revealed their biodegradability and enhanced bone formation.Our study demonstrated the favorable mechanical properties,biocompatibility,and biodegradability of fabricated PMMA-hydrogel hybrid cements loaded with BMP-2,as well as their ability to improve osteogenesis,making them a promising material for use in PKP and PVP.
文摘A kinetic model was developed to describe the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA). The model was based on a polymerization mechanism,which included the atom transfer equilibrium for primary radical, the propagation of growing polymer radical, and the atom transfer equilibrium for the growing polymer radical. An experiment was carried out to measure the conversion of monomer, the number-average molecular weight of polymer and molecular weight distribution for the ATRP process of DMAEMA. The experimental data were used to correlate the kinetic model and rate constants were obtained. The rate constants of activation and deactivation in the atom transfer equilibrium for primary radical are 1.0×10^4L·mol^-1·s^-1 and 0.04L·mol^-1·s^-1, respectively. The rate constant of the propagation of growing polymer radical is 8.50L·mol^-1·s^-1, and the rate constants of activation and deactivation in the atom transfer equilibrium for growing polymer radical are 0.045L·mol^-1·s^-1 and 1.2×10^5L·mol^-1·s^-1, respectively. The values of the rate constants represent the features of the ATRP process. The kinetic model was used to calculate the ATRP process of DMAEMA. The results show that the calculations agree well with the measurements.
基金Sponsored by the National Science Foundation of China and CAEP(10676003)
文摘The 2,2-dinitropropyl methacrylate(DNPMA) was synthesized by esterification of α-methacrylic acid with 2,2-dinitropropanol.The free-radical bulk polymerization of DNPMA in the presence of 2,2-azobisisobutyronitrile(AIBN) was investigated by differential scanning calorimetry(DSC) in the nonisothermal mode.Kissinger,Ozawa and Barrett methods were applied to determine the activation energy(Ea) and the reaction order of the free-radical polymerization.The results showed that the temperature of exothermic polymerization peaks increased with increasing heating rate.With increasing the molar ratio of monomer/initiator and the heating rate,the reaction order of nonisothermal polymerization was approximately equal to 1.The average Ea value from Kissinger and Ozawa methods(77.74±1.07 kJ/mol) was smaller than the value from the Barrett method(Ea=102.36 kJ/mol).
文摘A novel methacrylate monomer with bulky side group, tri(2-pyridyl)methyl methacrylate (Tr2PyMA), was synthesized and polymerized. The polymer obtained by radical polymerization exhibits high isotactic tacticity.
文摘A new kind of polymethyl methacrylate (PMMA)-TiO2 nanocomposite was synthesized through polymerization. The thermal and photic stability of this PMMA TiO2 nanocomposites were investigated. The as prepared samples were characterized by scanning electron microscopy (SEM), UV-Vis spectroscopy, differential thermal analysis (DTA) and the photo-induced weight loss, The results show that the photostability of the PMMA-TiO2 nanocomposite is higher than that of the pure PMMA under UV-light irradiation, The weight loss of the pure PMMA reaches 30 % after 300 h UVirradiation, while the composite only 0.3% under the identical experimental condition. The glass transition temperature (TR) of pure PMMA is only 80℃, while the Tg of the composite reaches 258℃. Compared with pure PMMA, the thermal stability of the composite is greatly enhanced.
文摘Silicone rubber films were modified by the consecutive grafting of 2-(diethylamino)ethyl methacrylate (DEAEMA) and N-vinylcaprolactam (NVCL) using direct method on two steps with gamma-rays. The effect of absorbed dose and monomer concentration on grafting degree was determined. The grafted samples were verified by FTIR-ATR spectroscopy and swelling;thermal properties were analyzed by DSC and TGA. The stimuli-responsive behavior was studied by swelling and/or DSC. Thermo- and pH-sensitive films of (PP-g-DEAEMA)-g-NVCL presented a pH critical at 3.2 and LCST around 63.5℃.
基金the National Natural Science Foundation of China(No.20372018)
文摘An efficient protocol for the synthesis of N^6-(2-Hydroxyethyl)adenosine and its analogues through nucleophilic substitution was developed. All the reactions were completed in 10 rain under microwave irradiation. Using water as solvent makes our method eco-friendly and easy to handle with.
基金financially supported by the National Key Research and Development Program of China(2019YFC1908204)the National Natural Scientific Fund of China(No.21878292,21776289,21908232,21978291)+1 种基金Innovation Academy forGreen Manufacture,Chinese Academy of Sciences(No.IAGM2020C12,IAGM2020C21 and IAGM-2019-A06)K.C.Wong Education Foundation(No.GJTD-2018-04)。
文摘Studies on the degradation process of waste polyethylene terephthalate(PET)have become increasingly mature,but there are relatively few studies on the separation of degradation products.The products contain many components and the separation of which is difficult.Therefore,the study on phase equilibrium thermodynamics of bis-2-hydroxyethyl terephthalate(BHET)is of great theoretical significance and practical value to provide basic data for the BHET crystallization separation.In this work,the degraded products were purified and characterized.The solubility of BHET in methanol,ethanol,ethylene glycol,water and the mixture of ethylene glycol+water were determined by static method.The experimental results were correlated with different models,such as ideal solution(IS)model,λh equation,Apelblat equation and NRTL model.Based on the van’t Hoff equation,the mixing Gibbs energy,enthalpy and entropy were calculated.From this work,the basic data which can be used to guide the crystallization process of BHET were obtained,including solubility data,correlation model and thermodynamic properties.
文摘The copolymerization of 2-hydroxyethyl acrylate (HEA, M//1) and methyl methacrylate (MMA, M//2) in cyclohexanone was studied. The multiple experiments of solution copolymerization with low conversion were carried out at two sensitive composition feed points at 60, 80, 100, 120 and 140 degree C, respectively. The composition of the copolymers was analyzed by **1H-NMR. The reactivity ratios which were estimated by the Error-in-Variable Method (EVM) of Mayo-Lewis equation were found to be r//1 equals 0.328, r//2 equals 1.781 for 60 degree C; 0.375, 1.709 for 80 degree C; 0.406, 1.654 for 100 degree C; 0.439, 1.540 for 120 degree C and 0.455, 1.400 for 140 degree C, and the 95% joint confidence intervals of the reactivity ratios were also determined. According to r//1 and r//2, Arrhenius relations and the activity energy difference between the homo- and cross-propagation were calculated. (Author abstract) 12 Refs.
基金The project was supported by the National Natural Science Foundation,Grant approval numbers 29472074 and 29632003
文摘Polyfluoroalkyl substituted 2-hydroxyethyl acrylate 6 was synthesized in six steps usingglycerol as a starting material. A preliminary investigation has been taken on the synthesisand characterization of copolymers of 6 and 2-hydroxyethyl methacrylate.
基金This project is supported by the National Natural Science Foundation of China and the President Foundation of Academia Sinica
文摘Optically active copolymers of pairs of three monomers, triphenyl (methyl methacrylate)and one or two pyridyl substituted methyl methacrylate homologues, were obtained by helix-sense-selective copolymerization using complexes of organolithium with chiral ligand as anionicinitiators in toluene at low temperature. The copolymers obtained with (-)-sparteine (Sp) and(S,S)-(+)-and (R, R)-(-)-2, 3-dimethoxy-1, 4-bis (dimethylamino) butanes((+)-and (-)-DDB) complexes of organolithium showed low optical activity, but PMP complex with N, N-diphenylethyleneamine monolithium amide (PMP-DPEDA-Li) was effective in synthesizingcopolymers of high optical rotation ([α]_D^(25) about+320~1370°)which were comparable to thoseof relative homopolymers with one-handed helical structure.
基金the National 863 Program(No.2003AA323030)the National Natural Science Foundation of China(No.50272069 and No.20472090)for financial support.
文摘Lithium aluminium amide [LiAI(NHR)4] 5 obtained by treating the primary amine 4 with LiAlH4 could promote the ring opening of epoxide 2 and led to high regioselective product of racemic bis[2-(6-fluoro-2-chromanyl)-2-hydroxyethyl]amine methanesulfonic acid salt 7.