首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
以L-赖氨酸为原料,先制备Nε-苄氧羰基-L-赖氨酸,光气法合成Nε-苄氧羰基-L-赖氨酸-N-羧酸酐[Lys-(Z)-NCA]。以聚乙二醇单甲醚(MPEG)为原料,制备了端氨基聚乙二醇单甲醚(MPEG-NH2),并以此为大分子引发剂,在氯仿中引发Lys-(Z)-NCA开环聚合,经无水溴化氢脱苄,合成不同组成和分子量的聚乙二醇单甲醚-聚L-赖氨酸嵌段共聚物。用IR1、H-NMR、GPC、DSC等对共聚物结构进行了表征。结果表明:MPEG-NH2引发Lys-(Z)-NCA开环聚合得到的是嵌段共聚物,通过1H-NMR谱计算得到了共聚物MPEG-PLL-1、MPEG-PLL-2、MPEG-PLL-3、MPEG-PLL-4中PLL链段的摩尔分数分别为0.553、0.795、0.848、0.861,共聚物数均分子量(Mn)分别为2.3×104、6.1×104、8.6×104、9.5×104。  相似文献   

2.
采用过氧化氢硫酸亚铁的氧化还原引发体系,首先使苯乙烯(St)在乳液聚合体系中进行均聚合,制得了端羟基聚苯乙烯(PSt-OH),然后将PSt-OH增溶于十二烷基硫酸钠的胶束溶液中,在硫酸铈铵的引发作用下,使水溶液中的N乙烯基吡咯烷酮(NVP)在PSt-OH端羟基部位发生嵌段共聚合,制得了双亲嵌段共聚物PSt-b-PVP。采用红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)、差示扫描量热(DSC)等手段对嵌段共聚物的组成与结构进行了表征。结果表明:在Ce(Ⅳ)盐的氧化作用下,增溶于胶束中的端羟基聚苯乙烯端会在端基产生自由基,顺利地实现NVP的嵌段共聚合反应。随着共聚合时间的延长,共聚物PSt-b-PVP大分子链中亲水嵌段PVP的比例不断增大。  相似文献   

3.
为研究极性调节剂对反应挤出苯乙烯类共聚物微观结构的影响,以双螺杆挤出机为反应器,有机锂为引发剂,四氢呋喃(THF)为极性调节剂,采用苯乙烯/异戊二烯(S/I)混合单体一次加料反应挤出技术合成了S/I共聚物,1H-NMR、GPC、DMA和TEM的分析结果表明:THF提高了共聚物的3,4-结构异戊二烯含量,使分散相尺寸变得细小且均匀,两相相容性提高;共聚物链段中长嵌段聚苯乙烯含量较少,并与大量分布较均匀的聚苯乙烯短嵌段、聚异戊二烯短嵌段以及无规共聚的苯乙烯单元共同组成完整的分子链。  相似文献   

4.
通过丙烯酸叔丁酯的自由基调聚和苯乙烯的原子转移自由基聚合(ATRP)法合成了聚丙烯酸叔丁酯-聚苯乙烯(PtBA-b-PS)嵌段共聚物,然后在三氟乙酸作用下进行选择性水解得到了两亲性聚丙烯酸-聚苯乙烯(PAA-b-PS) 嵌段共聚物。利用1H-NMR、FT-IR和GPC对产物的结构进行了表征。采用透析法制备了PAA-b-PS胶束,并利用激光纳米粒度仪和TEM观测了胶束的形态和大小,考察了PS嵌段的分子量对胶束大小的影响。结果表明:嵌段共聚物PAA-b-PS在水中自组装形成球状胶束,胶束平均粒径为140~190 nm,并随PS嵌段分子量的增加而增大,且粒径分布较窄。  相似文献   

5.
采用动态密度泛函理论(DDFT)方法对两嵌段和三嵌段共聚物熔体微相分离后的三维介观结构进行了模拟研究,考察了共聚物链长.N—12下组分A、B不同配比的11种两嵌段共聚物和10种三嵌段共聚物,通过等密度面图很好地表述了微相分离后的三维介观结构。通过比较序参数户、自由能F和熵S随时间的变化,发现当组分A与组分B的链节数之比.NA/NB和模拟参数均相同时,两嵌段共聚物熔体比三嵌段共聚物熔体容易发生微相分离,而三嵌段共聚物越不对称,微相分离越容易。  相似文献   

6.
通过原子转移自由基聚合反应(ATRP)合成了含刚性聚苯乙烯(PS)链段的聚(甲基丙烯酸甲酯-b-苯乙烯)嵌段共聚物(PMMA-b-PS)。用红外光谱、核磁共振氢谱和凝胶渗透色谱分析了该共聚物的化学结构、分子量及其分布。结果表明:PMMA-b-PS的数均分子量为2.69×105,分子量分布为1.53。以合成的PMMA-b-PS为基体,通过溶液浇铸法制备凝胶聚合物电解质(GPE)薄膜,研究了其电导率。PMMA-b-PS质量分数为40%的GPE具有较好的成膜性和导电性,室温下其电导率为8.82×10-5 S/cm;热失重分析表明,该GPE在质量损失5%时的热分解温度为139 °C,比相应的纯PMMA基GPE高49 °C。  相似文献   

7.
将均聚物聚苯乙烯(PS)与三嵌段共聚物聚异戊二烯聚苯乙烯聚乳酸(PIPSPLA)以一定摩尔比共混,采用原子力显微镜(AFM)研究了均聚物浓度对其薄膜样品中微纳米结构的影响。结果表明:当n(PS)∶n(PIPSPLA)为1∶2和1∶1时,薄膜呈现出规则排列的柱状微结构,且柱状微区的尺寸较混合前的样品有所改变;当n(PS)∶n(PIPSPLA)为2∶1时,PS与嵌段共聚物PIPSPLA的分子链发生了相分离,其中均聚物PS相形成了较大尺寸的岛状微区。  相似文献   

8.
本文采用 DSC技术,系统地研究了具有不同形态结构的聚苯乙烯-聚异戊二烯二嵌段共聚物的玻璃化转变及其微相分离行为。研究表明:PI相的玻璃化转变温度T_(g1)高于纯PI的T_g,并随PI嵌段子量的降低而略有升高;由PS组成基体(PS含量高)的嵌段共聚物的T_(g1)低于由PI组成基体(PS含量低)的嵌段共聚物的T_(g1),PS相的玻璃化转变温度T_(g2)低于纯PS的T_g,并随 PS嵌段分子量的降低而显著下降;由PS组成基体(PS含量高)的嵌段共聚物的T_(g2)高于白PI组成基体(PS含量低)的嵌段共聚物的T_(g2)。以上实验事实均可由在分相界面区内以化学链相连的PS与PI链段间的相互作用及其对PS与PI链段运动的影响予以解释。  相似文献   

9.
以正丁基锂(n-BuLi)为引发剂,苯乙烯(St)、异戊二烯(Ip)混合物为单体,十二烷基苯磺酸钠(SDBS)、四氢呋喃(THF)为极性调节剂,在双螺杆挤出机中,应用反应挤出技术实现了聚异戊二烯(PI)质量分数高达60%左右的苯乙烯 异戊二烯共聚物(S-I)的阴离子本体嵌段聚合。通过选择性氧化降解与GPC、1H-NMR、DMA和TEM结合,分析了产物的分子链结构。结果显示,SDBS和THF的加入增加了PI的3,4 结构含量,且大大限制了St的聚合,使最长聚苯乙烯(PS)嵌段的分子量大为减小,同时很难包裹大的Ip气泡,共聚物的结构主要为S-I小嵌段,两组分相容性增强,无规化程度增加。  相似文献   

10.
以S,S′-二(α,α′-二甲基-α″-乙酸)三硫代碳酸酯(TRIT)为链转移剂,利用可逆加成断裂链转移自由基聚合(RAFT)制备了窄分布的端羧基大分子链转移剂——聚苯乙烯和聚丙烯腈。以大分子链转移剂为RAFT试剂,引发苯乙烯或丙烯腈单体的RAFT聚合,进一步得到聚丙烯腈 聚苯乙烯 聚丙烯腈(PAN b PS b PAN)和聚苯乙烯 聚丙烯腈 聚苯乙烯(PS b PAN b PS)三嵌段共聚物。通过1H NMR、FT IR、凝胶渗透色谱(GPC)对所得产物的结构和分子量进行了表征,通过原子力显微镜(AFM)和拉曼光谱(Raman)研究了嵌段共聚物薄膜的微相分离结构与热解行为。结果表明:所得产物中除PAN b PS b PAN外,分子量分布均小于1.2。嵌段共聚物薄膜经250 ℃热稳定化与600 ℃热解处理后,碳化并形成了规整的石墨结构,微区尺寸在75 nm左右。  相似文献   

11.
FOR anesthesiologis s ,treatingpostoperativepainhas alwaysbeen a problem.Althoughopioidshave been provedtobe effective,theirsideeffectscouldnotbeignored.With thedevelopmentofscienceand pharmacology,many drugs with aspectsof satisfactoryanalgesicefficacyand couldbe welltoleratedby patientshave been developed.And lornoxicamisone of them, which isa non-steroidalanti-inflammatorydrug (NSAID ), with analgesic, anti-infl-ammatory,andantipyreticproperties.Itseliminationhalf-time(3 to 5 hours) isle…  相似文献   

12.
Dr.Zhang Ren,the chief physician,is the chairman of Shanghai Acupuncture and Moxibustion Association.Having been engaged in medicine for about 40 years,he is experienced in treating various intractable diseases.In his long years of clinical practice,he advocates taking the TCM differentiation as the basis to seek for the acupuncture method for treatment of modern intractable diseases.The author of this essay had the fortune to follow Dr.Zhang in study.The following is a summary of Dr.Zhang's experience in the acupuncture treatment for different intractable diseases with the same therapeutic principle.  相似文献   

13.
In treating chronic nephropathy,Luo Lingjie,a chief physician,pays attention to regulating the balance between yin and yang,treating infection if present,and removing pathogenic factors.He prescribes gentle drugs and uses carefully strongly warming-tonifying ones,emphasizes the importance of persuading the patient to persist in treatment with medication and nurse one's health for recuperation,and is good at combined use of TCM and western medicine therapy and brings the merits of various therapies into full play,with obvious theraoeutic effects.  相似文献   

14.
Objective: To observe the therapeutic effects in acupunture treatment of primary dysmenorrhea combined with spinal Tui Na, and study its mechanism. Methods: Thirty cases of the treatment group were treated by acupuncture combined with spinal Tui Na, and thirty cases in the control group were treated by routine acupuncture. Results: The total effective rate was 93.3% in the treatment group, and 73.3% in the control group, with a significant difference between the two groups (P<0.05). Conclusions: Acupuncture combined with spinal Tui Na has good prospects for treatment of primary dysmenorrhea.  相似文献   

15.
16.
目的 探讨猪肺磷脂注射液联合经鼻持续气道正压通气(NCPAP)对呼吸衰竭早产儿的临床疗效及肌酸激酶同工酶活性(CK-MB)的影响.方法 选取呼吸衰竭早产儿80例,分为观察组和对照组各40例.对照组采用NCPAP给氧治疗,观察组给予NCPAP给氧联合猪肺磷脂气管内给药.观察两组患儿治疗前及治疗12h、24 h后PaO2、PaCO2、血氧饱和度(SaO2)、pH的变化情况,检测治疗前及治疗5d后血清CK-MB水平;评估两组患儿的临床治疗效果.结果 两组患儿PaO2、PaCO2、SaO2、pH比较,差异均有统计学意义(P<0.05),其中观察组治疗后的PaO2、SaO2、pH均高于对照组,PaCO2则低于对照组.两组的PaO2、SaO2、pH均随观察时间延长而升高(P<0.05),PaCO2均随观察时间的延长而降低(P<0.05).观察组治疗有效率为87.5%,显著高于对照组的70.0% (P <0.05).治疗5d后两组患儿血清CK-MB水平均较前降低(P<0.05),且观察组明显低于对照组(P<0.05).结论 猪肺磷脂注射液气管内给药联合NCPAP可以显著降低呼吸衰竭早产儿CK-MB的含量,提高治疗有效率,起到很好的呼吸循环支持作用.  相似文献   

17.
Evidence obtained from randomized controlled trials (RCTs) has been generally accepted as the gold standard in the evaluation of clinical effectiveness. Readers need to understand the trial design, implementation, results, analysis and interpretation, so as to fully Jnderstand the results of RCTs. Thus, the investigators of RCTs have to report these items in a complete, accurate and clear manner. Since 1998, we have conducted several evaluations on the reporting quality of RCTs published in Chinese journals on traditional Chinese medicine (TCM) and results have shown that there is an urgent need for higher quality RCTs on TCM.  相似文献   

18.
Ankylosing spondylitis is a chronic and progressive disorder with inflammation mainly involving the central axis joints. It mainly affects the cervical spine and the lumbosacral area, with the pathogenesis closely related to the kidney and the Governor Vessel (GV). TCM holds that the syndrome is deficiency in origin and excess in superficiality, which is due to insufficiency of the kidney, deficiency of GV, and blocking of the channels with the invasion of exogenous evil, leading to poor circulation of qi and blood and malnutrition of the bones, muscles and joints. The TCM method of tonifying the kidney and strengthening GV to regulate circulation of qi and blood and check the arthralgia pain should be adopted, with the Kidney-Tonifying and GV Strengthening Decoction (益肾强督汤) prescribed.  相似文献   

19.
20.
CHEMOTHERAPY playsa greatrolein the treat- ment of malignanttumors,especiallyingynecolo- gicalones.But inanticancerchemotherapy,leuko-cytopeniaisfrequentlytheprimarydose-limitingsideeffect factor.Moreover,cancersarefrequentlychemoresistantbe-causeof overexpressionof P-glycoprotein(P-gp), which isencodedby multidrugresistancegene (MDR1 ) and detectableinup to50% ofhuman cancersand renderscellsresistancetoanticancerdrugs.The safetyand potentialtherapeuticbenefitof mdr1 gene transferredto h…  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号