沉淀聚合包覆硝酸铵的吸湿性研究

在环己烷介质中采用丙烯腈单体沉淀聚合反应对硝酸铵进行了包覆,测试了包覆前后硝酸铵的吸湿性、结块性,利用扫描电子显微镜观察了包覆效果,利用接触角测试仪测量了AN在不同测试液中的接触角,分析了改性后硝酸铵吸湿性降低的原因和机理。     

宽带中国战略下一户多机的研究和实践

随着国家"宽带中国"战略的发布,高接入带宽为一户多机创造了良好的条件。同时,用户个性化需求日益强烈,家庭内手机、PAD、机顶盒、电脑多种终端使用视频服务等宽带业务将成为常态。文章分析一户多机面临的挑战,提出运营商在一户多机时代的应变之道。     

Ultrahigh Electrical Resistance of Poly(cyclohexyl methacrylate)/Carbon Nanotube Composites Prepared Using Surface‐Initiated Polymerization

Multiwalled carbon nanotubes on which poly(cyclohexyl methacrylate)s are densely grafted (PCHMA‐CNTs), are synthesized using a modified surface‐initiated atom transfer radical polymerization technique. The electrical resistance of PCHMA‐CNT is systematically characterized under direct current (DC) and alternating current and compared to that of conventional nanocomposites prepared by blending PCHMA with the CNT (PCHMA/CNT). At a comparable volume fraction of CNT, DC volume resistivity of PCHMA‐CNT is 14 orders of magnitude higher than that of PCHMA/CNT. This is because the grafted polymer with a combination of the high molecular weight and the high grafting density isolates individual CNTs at a long distance in the PCHMA‐CNT system. In addition, impedance analysis reveals that the highly insulated PCHMA‐CNT has the same electrical nature as neat PCHMA, i.e., it is a dielectric. Furthermore, dynamic mechanical analysis shows PCHMA‐CNT has a good mechanical properties as well as ultrahigh electrical resistance.     

Photo‐Induced Functionalization of Spherical and Planar Surfaces via Caged Thioaldehyde End‐Functional Polymers

The synthesis and application of a novel reversible addition‐fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λ_max = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol^?1 ≤ M_n ≤ 15 000 g mol^?1; 1.07 ≤ ? ≤ 1.20) with excellent end‐group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels–Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene‐reactive polymeric microspheres. The grafted particles are in‐depth characterized via scanning electron microscopy, elemental analysis, X‐ray photoelectron spectroscopy, and high resolution FT‐IR microscopy, leading to a qualitative as well as quantitative image of the core–shell objects. Grafting densities up to 0.10 molecules nm^?2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)‐coated glass slides and silicon wafers via two‐photon direct laser writing (DLW) imaged by ToF‐SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub‐micrometer resolution.     

超低醛网印粘合剂的合成与应用

采用核壳聚合机理,用Ｎ,Ｎ‘－亚甲基双丙烯酰胺作互穿聚合物网络的交联剂,以达到盐－还原剂体系将高活性的环氧基单体接入高分子上,从而得到超低醛,核软壳硬,且各项性能较优的自交联网印粘合剂。     

端羟基聚环氧氯丙烷醚的合成及表征

采用乳液双金属氰化物络合物代替Lewis酸类作为催化剂,使环氧氯丙烷(ECH)开环聚合,制得相对分子质量较高及分子质量分布较窄的聚环氧氯丙烷(PECH),这种PECH可用于高质量的含能叠氮粘合剂中。研究了影响ECH聚合的一些关键因素,包括引发剂的类型及用量,单体的加料方式及催化剂用量等。实验结果表明,PECH的官能度随引发剂的种类而变。而增加催化剂用量及提高反应温度,则可增大PECH的相对分子质量。另外,连续地逐滴加入单体比一次性加入单体较优。当以双酚A为引发剂,催化剂用量为生成PECH量的0.05%,反应温度为128℃时,PECH的收率可大于95%,所得PECH的官能度为2～3,PECH的结构由IR、1HNMR及GPC确认。     

PBT的固相缩聚的工艺研究

本文用固相缩聚的方法合成了高分子量ＰＢＴ,并研究了温度,时间对ＰＢＴ固相缩聚反应速度的影响;同时还用ＤＳＣ法分析了所合成ＰＢＴ的熔融行为。     

Bar-coated high-performance organic thin-film transistors based on ultrathin PDFDT polymer with molecular weight independence

We report high-performance organic thin-film transistors (OTFTs) with an ultrathin active layer of difluorobenzothiadiazole-dithienosilole copolymer (PDFDT) form by using the wire bar-coating process. The top-gate/bottom contact (TG/BC) OTFTs based on bar-coated PDFDT polymer as channel material and poly(methyl methacrylate) (PMMA) as gate dielectric show a hole mobility of up to 2.2 cm² V⁻¹s⁻¹ with a current ON/OFF ratio (I_on/I_off) of 10⁴∼10⁵, with the mobility being two times larger than that of the spin-coated PDFDT based OTFTs. The higher mobility of the bar-coated PDFDT polymer films can be attributed to the well-organized fibril structures of the polymer chains. Importantly, two different molecular weight polymers (M_n = 23 and 34 kDa) were employed to conduct these experiments and both batches showed about the same performance, which mitigates the typical batch-to-batch variation in OTFT performance. Furthermore, we explored the operational stability of the bar-coated OTFTs in ambient air and nitrogen environments. The bias-stress and cycling tests between the ON/OFF states of the bar-coated devices showed high stability in both nitrogen and air. Conclusively, here we demonstrate that (i) a simple bar-coating process is a better method to control and obtain good polymer morphology in comparison to spin-coating, and (ii) the PDFDT polymer has great potential to provide good reproducibility and stability in large-area OTFT devices.     

农村信息化讨论--资源的整合和利用

本文系统分析了当前农村信息化建设现状,以广西部分县镇为例。指出了目前存在的问题,根据现有条件提出了相应的对策与建议。对其他一些地区有效实施农村信息化有一定的借鉴作用。