Colloidal mesoporous silica nanoparticles functionalized with carboxy-terminated polyethylene glycol(CMS-PEG-COOH) were successfully synthesized by covalently grafting dicarboxy-terminated polyethylene glycol(HOOC-PEG...Colloidal mesoporous silica nanoparticles functionalized with carboxy-terminated polyethylene glycol(CMS-PEG-COOH) were successfully synthesized by covalently grafting dicarboxy-terminated polyethylene glycol(HOOC-PEG-COOH) on the surface of the amino functionalized CMS nanoparticles with amide bond as a cross linker. Moreover, the structural and particle properties of CMS-PEG-COOH were characterized by nuclear magnetic resonance spectroscopy(1 H-NMR), transmission electron microscopy(TEM), dynamic light scattering(DLS), nitrogen adsorption-desorption measurements, X-ray diffraction(XRD), and Fourier transform infrared spectroscopy(FT-IR). The nanomaterials presented a relatively uniform spherical shape morphology with diameters of about 120 nm,and favorable dispersibility in weak acid solution. The CMSPEG-COOH exhibited no changes in the state of amorphous, while the mesopores sizes of 5.25 nm might provide the nanomaterials with large capacity for the loading and releasing of drugs. So the results indicated that CMSPEG-COOH might be a critical nanomaterial for drug delivery system in the future.展开更多
The main principle and the characteristic of Predictive Functional Control (PFC) strategy are presented in this paper and the corresponding control system aid design software APC-PFC is also introduced. For a chlorina...The main principle and the characteristic of Predictive Functional Control (PFC) strategy are presented in this paper and the corresponding control system aid design software APC-PFC is also introduced. For a chlorinated polyethylene (CPE) process, a design scheme of cascade predictive functional control system is described and the control performance is improved obviously.展开更多
AIM: To investigate the effects of lubiprostone and Polyethylene Glycol 3350 (PEG) on mucosal barrier repair in ischernic-injured porcine intestine. METHODS: Ileum from 6 piglets (approximately 15 kg body weight...AIM: To investigate the effects of lubiprostone and Polyethylene Glycol 3350 (PEG) on mucosal barrier repair in ischernic-injured porcine intestine. METHODS: Ileum from 6 piglets (approximately 15 kg body weight) was subjected to ischemic conditions by occluding the local rnesenteric circulation for 45 min in vivo. Ileal tissues from each pig were then harvested and mounted in Ussing chambers and bathed in oxygenated Ringer's solution in vitro. Intestinal barrier function was assessed by measuring transepithelial electrical resistance (TER) and mucosal-to-serosal fluxes of ^3H-rnannitol and ^14C-inulin. Statistical analyses of data collected over a 120-min time course included 2-way ANOVA for the effects of time and treatment on indices of barrier function. RESULTS: Application of 1μmol/L lubiprostone to the rnucosal surface of ischemic-injured ileum in vitro induced significant elevations in TER compared to nontreated tissue. Lubiprostone also reduced mucosal-toserosal fluxes of ^3H-rnannitol and ^14C-inulin. Alternatively, application of a polyethylene laxative (PEG, 20 rnmol/L) to the mucosal surface of ischernic tissues significantly increased flux of ^3H-rnannitol and ^14C-inulin. CONCLUSION: This experiment demonstrates that lubiprostone stimulates recovery of barrier function in ischemic intestinal tissues whereas the PEG laxative had deleterious effects on mucosal repair. These results suggest that, unlike osmotic laxatives, lubiprostone stimulates repair of the injured intestinal barrier.展开更多
Through kinetic method, the reaction mechanism and the rate equations of chlorination of polyethylene are suggested in this paper. The rate of chlorination is second order with respect to the concentration of methylen...Through kinetic method, the reaction mechanism and the rate equations of chlorination of polyethylene are suggested in this paper. The rate of chlorination is second order with respect to the concentration of methylene remained and chlorine, respectively. Apparent changes in crystallinity during chlorination processes were determinated by differential scanning calorimetry(DSC). The mathematical model relating crystallinety with kinetic parameters and function of sequence length distribution are derived.展开更多
As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this wor...As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this work,the density functional theory(DFT)calculation combined with paired interacting orbitals(PIO)method was applied for the theoretical studies on coordination reaction mechanism between ethylene monomer and two model catalysts namely Cr(Ⅱ)(OH)_2(M1) and silsesquioxane-supported Cr(Ⅱ)(M2)as surfac...展开更多
Chemical modification of MWCNTs via oxidation followed by side wall functionalization using polyethylene glycol (PEG) and octadecylamine (ODA), separately, was studied. Different characterization techniques such a...Chemical modification of MWCNTs via oxidation followed by side wall functionalization using polyethylene glycol (PEG) and octadecylamine (ODA), separately, was studied. Different characterization techniques such as FTIR spectrometery, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and solubility in different solvents were performed for the oxidized MWCNTs, MWCNTs-PEG and MWCNTs-ODA. The characterization techniques proved the presence of the functional groups on the MWCNTs surface. Thermal gravimetric analysis revealed that nearly 16% (by weight) of the MWCNTs were functionalized with PEG and 39% (by weight) was functionalized with ODA.展开更多
Constipation is a significant sociomedical problem,which can be caused by various reasons.In the diagnostic approach to patients with constipation,the following data are usually sufficient:History,complete physical ex...Constipation is a significant sociomedical problem,which can be caused by various reasons.In the diagnostic approach to patients with constipation,the following data are usually sufficient:History,complete physical examination(including rectal examination),and additional diagnostic tests.A colonoscopy is not a necessary diagnostic method for all patients with constipation.However,if patients have alarm symptoms/signs,that suggest an organic reason for constipation,a colonoscopy is necessary.The most important alarm symptoms/signs are age>50 years,gastrointestinal bleeding,new-onset constipation,a palpable mass in the abdomen and rectum,weight loss,anemia,inflammatory bowel disease,and family history positive for colorectal cancer.Most endoscopists do not like to deal with patients with constipation.There are two reasons for this,namely the difficulty of endoscopy and the adequacy of preparation.Both are adversely affected by constipation.To improve the quality of colonoscopy in these patients,good examination techniques and often more extensive preparation are necessary.Good colonoscopy technique implies adequate psychological preparation of the patient,careful insertion of the endoscope with minimal insufflation,and early detection and resolution of loops.Bowel preparation for colonoscopy often requires prolonged preparation and sometimes the addition of other laxatives.展开更多
目的通过比较聚乙二醇洛塞那肽与利拉鲁肽治疗肥胖2型糖尿病的疗效,为临床治疗该类疾病选择更高效的用药方案。方法选取东南大学医学院附属南京同仁医院2022年1月至2023年10月予以相应治疗的肥胖2型糖尿病患者共136例作为此次试验对象,...目的通过比较聚乙二醇洛塞那肽与利拉鲁肽治疗肥胖2型糖尿病的疗效,为临床治疗该类疾病选择更高效的用药方案。方法选取东南大学医学院附属南京同仁医院2022年1月至2023年10月予以相应治疗的肥胖2型糖尿病患者共136例作为此次试验对象,按照随机数字表法分成68例A组(聚乙二醇洛塞那肽治疗)与68例B组(利拉鲁肽治疗)。比较治疗前后两组肥胖相关指标、治疗前后两组血脂相关指标、治疗前后两组血糖指标以及治疗后不良反应发生率。结果治疗后两组体质量、腰臀比、体质量指数(BMI)和腰围均下降,B组体质量和BMI[分别为(80.31±7.62)kg和(24.13±1.82)kg·m^(-2)]低于A组体质量[分别为(83.65±7.93)kg和BMI(25.34±1.84)kg·m^(-2)](体质量:t=2.504,P=0.014;BMI:t=3.855,P<0.05);治疗后两组甘油三酯(TG)、血清总胆固醇(TC)和低密度脂蛋白(LDL)均下降,高密度脂蛋白胆固醇(HDL-C)上升(均P<0.05);治疗后两组餐后2 h血糖(2 h FBG)、空腹血糖(FBG)、糖化血红蛋白(HbAlc)、胰岛素抵抗指数(HOMA-IR)水平均下降,空腹血糖胰岛素(FINS)、β细胞功能指数(HOMA-β)水平均上升,A组2 h FBG、FBG[分别为(7.86±1.12)mmol·L^(-1)、(6.18±0.71)mmol·L^(-1)]低于B组[分别为2 h FBG(8.72±1.34)mmol·L^(-1)和FBG(7.02±0.62)mmol·L^(-1)](2 h FBG:t=4.061,P<0.05;FBG:t=7.349,P<0.05),A组HOMA-β[(74.62±3.78)%]高于B组[(62.79±3.56)%](t=18.937,P<0.05);两组不良反应发生率比较差异无统计学意义(20.59%vs 25.00%,χ^(2)=0.376,P=0.540)。结论对于肥胖2型糖尿病患者,聚乙二醇洛塞那肽与利拉鲁肽均能有效减轻体质量、调节血脂、降低血糖水平以及增强胰岛β细胞的功能,且安全性相似。然而,在降低体质量方面,利拉鲁肽的效果更为显著,而聚乙二醇洛塞那肽在改善胰岛β细胞功能和降低血糖方面则表现更为出色。展开更多
AIM To assess the knowledge of general pediatricians througout Indonesia about the diagnosis and treatment of childhood constipation.METHODS A comprehensive questionnaire was distributed to general pediatricians from ...AIM To assess the knowledge of general pediatricians througout Indonesia about the diagnosis and treatment of childhood constipation.METHODS A comprehensive questionnaire was distributed to general pediatricians from several teaching hospitals and government hospitals all over Indonesia.RESULTS Data were obtained from 100 pediatricians, with a mean of 78.34 ± 18.00 mo clinical practice, from 20 cities throughout Indonesia. Suspicion of constipation in a child over 6 mo of age arises when the child presents with a decreased frequency of bowel movements(according to 87% of participants) with a mean of one bowel movement per 3.59 ± 1.0 d, hard stools(83%), blood in the stools(36%), fecal incontinence(33%), and/or difficulty in defecating(47%). Only 26 pediatricians prescribe pharmacologic treatment as first therapeutic approach, while the vast majority prefers nonpharmacologic treatment, mostly(according to 68%) The preferred nonpharmacologic treatment are high-fiber diet(96%), increased fluid intake(90%), toilet training(74%), and abdominal massage(49%). Duration of non-pharmacological treatment was limited to 1 to 2 wk. Seventy percent of the pediatricians recommending toilet training could only mention some elements of the technique, and only 15% was able to explain it fully and correctly. Lactulose is the most frequent pharmacologic intervention used(87% of the participants), and rectal treatment with sodium citrate, sodium lauryl sulfo acetate, and sorbitol is the most frequent rectal treatment(85%). Only 51% will prescribe rectal treatment for fecal impaction. The majority of the pediatricians(69%) expect a positive response during the first week with a mean(± SD) of 4.1(± 2.56) d. Most participants(86%) treat during one month or even less. And the majority(67%) stops treatment when the frequency and/or consistency of the stools have become normal, or if the patient had no longer complaints.CONCLUSION These data provide an insight on the diagnosis and management of constipation in childhood in Indonesia. Although general pediatricians are aware of some important aspects of the diagnosis and mangement of constipation, overall knowledge is limited. Efforts should be made to improve the distribution of existing guidelines. These findings highlight and confirm the difficulties in spreading existing information from guidelines to general pediatricians.展开更多
Copolymerizations of ethylene and 1-dodecene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2(1a), [t-BuNSiMe2(2,7-^tBu2Flu)]TiMe2(1 b), and [(1-adamantyl)NSi...Copolymerizations of ethylene and 1-dodecene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2(1a), [t-BuNSiMe2(2,7-^tBu2Flu)]TiMe2(1 b), and [(1-adamantyl)NSiMe2(2,7-^tBu2Flu)]TiMe2(1c) activated by modified methylaluminoxane. The activity increased by the introduction of the alkyl groups on the fluorenyl and amido ligands, and 1c produced the highest molecular weight copolymers. Complex 1c also promoted copolymerization of ethylene and ^iBu3 Al protected 10-undecen-1-ol with high activity(~2000 kg·mol^-1·h^-1), affording hydroxy-functionalized ultrahigh molecular weight polyethylene. The hydroxy content of the copolymers obtained was controllable by changing comonomer feed ratio. The introduction of a small amount of hydroxy group can alter the surface properties of polyethylene.展开更多
以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)改性的硫酸钙晶须(CSW)为高密度聚乙烯(HDPE)的填料,采用熔融共混法制备了HDPE/CSW复合材料。通过SEM、XRD、TG、DSC表征了KH570改性的CSW对复合材料HDPE/CSW的性能影响。结果表明,改性CSW...以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)改性的硫酸钙晶须(CSW)为高密度聚乙烯(HDPE)的填料,采用熔融共混法制备了HDPE/CSW复合材料。通过SEM、XRD、TG、DSC表征了KH570改性的CSW对复合材料HDPE/CSW的性能影响。结果表明,改性CSW质量分数为20%时,HDPE/CSW的拉伸和弯曲强度比纯HDPE分别增加9.28%和33.04%,且易产生异相结晶,提升了HDPE/CSW复合材料的耐热性和结晶度。纯HDPE的热降解反应活化能为244.11 k J/mol,改性CSW质量分数为50%时,HDPE/CSW复合材料的热降解反应活化能降到236.99 kJ/mol,表明CSW提升了HDPE/CSW复合材料的热降解反应速率,扩展了复合材料的使用范围。展开更多
基金Funded by the National Natural Science Foundation of China(No.81201197)
文摘Colloidal mesoporous silica nanoparticles functionalized with carboxy-terminated polyethylene glycol(CMS-PEG-COOH) were successfully synthesized by covalently grafting dicarboxy-terminated polyethylene glycol(HOOC-PEG-COOH) on the surface of the amino functionalized CMS nanoparticles with amide bond as a cross linker. Moreover, the structural and particle properties of CMS-PEG-COOH were characterized by nuclear magnetic resonance spectroscopy(1 H-NMR), transmission electron microscopy(TEM), dynamic light scattering(DLS), nitrogen adsorption-desorption measurements, X-ray diffraction(XRD), and Fourier transform infrared spectroscopy(FT-IR). The nanomaterials presented a relatively uniform spherical shape morphology with diameters of about 120 nm,and favorable dispersibility in weak acid solution. The CMSPEG-COOH exhibited no changes in the state of amorphous, while the mesopores sizes of 5.25 nm might provide the nanomaterials with large capacity for the loading and releasing of drugs. So the results indicated that CMSPEG-COOH might be a critical nanomaterial for drug delivery system in the future.
文摘The main principle and the characteristic of Predictive Functional Control (PFC) strategy are presented in this paper and the corresponding control system aid design software APC-PFC is also introduced. For a chlorinated polyethylene (CPE) process, a design scheme of cascade predictive functional control system is described and the control performance is improved obviously.
文摘AIM: To investigate the effects of lubiprostone and Polyethylene Glycol 3350 (PEG) on mucosal barrier repair in ischernic-injured porcine intestine. METHODS: Ileum from 6 piglets (approximately 15 kg body weight) was subjected to ischemic conditions by occluding the local rnesenteric circulation for 45 min in vivo. Ileal tissues from each pig were then harvested and mounted in Ussing chambers and bathed in oxygenated Ringer's solution in vitro. Intestinal barrier function was assessed by measuring transepithelial electrical resistance (TER) and mucosal-to-serosal fluxes of ^3H-rnannitol and ^14C-inulin. Statistical analyses of data collected over a 120-min time course included 2-way ANOVA for the effects of time and treatment on indices of barrier function. RESULTS: Application of 1μmol/L lubiprostone to the rnucosal surface of ischemic-injured ileum in vitro induced significant elevations in TER compared to nontreated tissue. Lubiprostone also reduced mucosal-toserosal fluxes of ^3H-rnannitol and ^14C-inulin. Alternatively, application of a polyethylene laxative (PEG, 20 rnmol/L) to the mucosal surface of ischernic tissues significantly increased flux of ^3H-rnannitol and ^14C-inulin. CONCLUSION: This experiment demonstrates that lubiprostone stimulates recovery of barrier function in ischemic intestinal tissues whereas the PEG laxative had deleterious effects on mucosal repair. These results suggest that, unlike osmotic laxatives, lubiprostone stimulates repair of the injured intestinal barrier.
文摘Through kinetic method, the reaction mechanism and the rate equations of chlorination of polyethylene are suggested in this paper. The rate of chlorination is second order with respect to the concentration of methylene remained and chlorine, respectively. Apparent changes in crystallinity during chlorination processes were determinated by differential scanning calorimetry(DSC). The mathematical model relating crystallinety with kinetic parameters and function of sequence length distribution are derived.
基金the National Natural Science Foundation of China(No.20744004 and No.20774025).
文摘As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this work,the density functional theory(DFT)calculation combined with paired interacting orbitals(PIO)method was applied for the theoretical studies on coordination reaction mechanism between ethylene monomer and two model catalysts namely Cr(Ⅱ)(OH)_2(M1) and silsesquioxane-supported Cr(Ⅱ)(M2)as surfac...
文摘Chemical modification of MWCNTs via oxidation followed by side wall functionalization using polyethylene glycol (PEG) and octadecylamine (ODA), separately, was studied. Different characterization techniques such as FTIR spectrometery, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and solubility in different solvents were performed for the oxidized MWCNTs, MWCNTs-PEG and MWCNTs-ODA. The characterization techniques proved the presence of the functional groups on the MWCNTs surface. Thermal gravimetric analysis revealed that nearly 16% (by weight) of the MWCNTs were functionalized with PEG and 39% (by weight) was functionalized with ODA.
基金Supported by the Ministry of Science,Technological Development and Innovations,Republic of Serbia,No.451-03-66/2024-03/200110.
文摘Constipation is a significant sociomedical problem,which can be caused by various reasons.In the diagnostic approach to patients with constipation,the following data are usually sufficient:History,complete physical examination(including rectal examination),and additional diagnostic tests.A colonoscopy is not a necessary diagnostic method for all patients with constipation.However,if patients have alarm symptoms/signs,that suggest an organic reason for constipation,a colonoscopy is necessary.The most important alarm symptoms/signs are age>50 years,gastrointestinal bleeding,new-onset constipation,a palpable mass in the abdomen and rectum,weight loss,anemia,inflammatory bowel disease,and family history positive for colorectal cancer.Most endoscopists do not like to deal with patients with constipation.There are two reasons for this,namely the difficulty of endoscopy and the adequacy of preparation.Both are adversely affected by constipation.To improve the quality of colonoscopy in these patients,good examination techniques and often more extensive preparation are necessary.Good colonoscopy technique implies adequate psychological preparation of the patient,careful insertion of the endoscope with minimal insufflation,and early detection and resolution of loops.Bowel preparation for colonoscopy often requires prolonged preparation and sometimes the addition of other laxatives.
文摘目的通过比较聚乙二醇洛塞那肽与利拉鲁肽治疗肥胖2型糖尿病的疗效,为临床治疗该类疾病选择更高效的用药方案。方法选取东南大学医学院附属南京同仁医院2022年1月至2023年10月予以相应治疗的肥胖2型糖尿病患者共136例作为此次试验对象,按照随机数字表法分成68例A组(聚乙二醇洛塞那肽治疗)与68例B组(利拉鲁肽治疗)。比较治疗前后两组肥胖相关指标、治疗前后两组血脂相关指标、治疗前后两组血糖指标以及治疗后不良反应发生率。结果治疗后两组体质量、腰臀比、体质量指数(BMI)和腰围均下降,B组体质量和BMI[分别为(80.31±7.62)kg和(24.13±1.82)kg·m^(-2)]低于A组体质量[分别为(83.65±7.93)kg和BMI(25.34±1.84)kg·m^(-2)](体质量:t=2.504,P=0.014;BMI:t=3.855,P<0.05);治疗后两组甘油三酯(TG)、血清总胆固醇(TC)和低密度脂蛋白(LDL)均下降,高密度脂蛋白胆固醇(HDL-C)上升(均P<0.05);治疗后两组餐后2 h血糖(2 h FBG)、空腹血糖(FBG)、糖化血红蛋白(HbAlc)、胰岛素抵抗指数(HOMA-IR)水平均下降,空腹血糖胰岛素(FINS)、β细胞功能指数(HOMA-β)水平均上升,A组2 h FBG、FBG[分别为(7.86±1.12)mmol·L^(-1)、(6.18±0.71)mmol·L^(-1)]低于B组[分别为2 h FBG(8.72±1.34)mmol·L^(-1)和FBG(7.02±0.62)mmol·L^(-1)](2 h FBG:t=4.061,P<0.05;FBG:t=7.349,P<0.05),A组HOMA-β[(74.62±3.78)%]高于B组[(62.79±3.56)%](t=18.937,P<0.05);两组不良反应发生率比较差异无统计学意义(20.59%vs 25.00%,χ^(2)=0.376,P=0.540)。结论对于肥胖2型糖尿病患者,聚乙二醇洛塞那肽与利拉鲁肽均能有效减轻体质量、调节血脂、降低血糖水平以及增强胰岛β细胞的功能,且安全性相似。然而,在降低体质量方面,利拉鲁肽的效果更为显著,而聚乙二醇洛塞那肽在改善胰岛β细胞功能和降低血糖方面则表现更为出色。
文摘AIM To assess the knowledge of general pediatricians througout Indonesia about the diagnosis and treatment of childhood constipation.METHODS A comprehensive questionnaire was distributed to general pediatricians from several teaching hospitals and government hospitals all over Indonesia.RESULTS Data were obtained from 100 pediatricians, with a mean of 78.34 ± 18.00 mo clinical practice, from 20 cities throughout Indonesia. Suspicion of constipation in a child over 6 mo of age arises when the child presents with a decreased frequency of bowel movements(according to 87% of participants) with a mean of one bowel movement per 3.59 ± 1.0 d, hard stools(83%), blood in the stools(36%), fecal incontinence(33%), and/or difficulty in defecating(47%). Only 26 pediatricians prescribe pharmacologic treatment as first therapeutic approach, while the vast majority prefers nonpharmacologic treatment, mostly(according to 68%) The preferred nonpharmacologic treatment are high-fiber diet(96%), increased fluid intake(90%), toilet training(74%), and abdominal massage(49%). Duration of non-pharmacological treatment was limited to 1 to 2 wk. Seventy percent of the pediatricians recommending toilet training could only mention some elements of the technique, and only 15% was able to explain it fully and correctly. Lactulose is the most frequent pharmacologic intervention used(87% of the participants), and rectal treatment with sodium citrate, sodium lauryl sulfo acetate, and sorbitol is the most frequent rectal treatment(85%). Only 51% will prescribe rectal treatment for fecal impaction. The majority of the pediatricians(69%) expect a positive response during the first week with a mean(± SD) of 4.1(± 2.56) d. Most participants(86%) treat during one month or even less. And the majority(67%) stops treatment when the frequency and/or consistency of the stools have become normal, or if the patient had no longer complaints.CONCLUSION These data provide an insight on the diagnosis and management of constipation in childhood in Indonesia. Although general pediatricians are aware of some important aspects of the diagnosis and mangement of constipation, overall knowledge is limited. Efforts should be made to improve the distribution of existing guidelines. These findings highlight and confirm the difficulties in spreading existing information from guidelines to general pediatricians.
基金financially supported by the National Natural Science Foundation of China (No. 21174026)Program for New Century Excellent Talents in University+3 种基金the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning"Shu Guang" project supported by Shanghai Municipal Education CommissionShanghai Education Development Foundationthe Fundamental Research Funds for the Central Universities (No. CUSF-DH-D-2017041)
文摘Copolymerizations of ethylene and 1-dodecene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2(1a), [t-BuNSiMe2(2,7-^tBu2Flu)]TiMe2(1 b), and [(1-adamantyl)NSiMe2(2,7-^tBu2Flu)]TiMe2(1c) activated by modified methylaluminoxane. The activity increased by the introduction of the alkyl groups on the fluorenyl and amido ligands, and 1c produced the highest molecular weight copolymers. Complex 1c also promoted copolymerization of ethylene and ^iBu3 Al protected 10-undecen-1-ol with high activity(~2000 kg·mol^-1·h^-1), affording hydroxy-functionalized ultrahigh molecular weight polyethylene. The hydroxy content of the copolymers obtained was controllable by changing comonomer feed ratio. The introduction of a small amount of hydroxy group can alter the surface properties of polyethylene.
文摘以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)改性的硫酸钙晶须(CSW)为高密度聚乙烯(HDPE)的填料,采用熔融共混法制备了HDPE/CSW复合材料。通过SEM、XRD、TG、DSC表征了KH570改性的CSW对复合材料HDPE/CSW的性能影响。结果表明,改性CSW质量分数为20%时,HDPE/CSW的拉伸和弯曲强度比纯HDPE分别增加9.28%和33.04%,且易产生异相结晶,提升了HDPE/CSW复合材料的耐热性和结晶度。纯HDPE的热降解反应活化能为244.11 k J/mol,改性CSW质量分数为50%时,HDPE/CSW复合材料的热降解反应活化能降到236.99 kJ/mol,表明CSW提升了HDPE/CSW复合材料的热降解反应速率,扩展了复合材料的使用范围。