苯乙烯和甲基丙烯酸甲酯梯度共聚物的合成

以2－溴异丁酸乙酯为引发剂,溴化亚酮／联二吡啶／铜为催化剂,通过原子转移自由基聚合（ATRP）以及连续补加第二单体的方法制备苯乙烯（St)－甲基丙烯酸甲酯（MMA）梯度共聚物。共聚物相对分子质量的可控性和窄分布证明这是一种活性聚合过程,反应过程中聚合物链的组成变化情况说明形成了梯度结构;聚合温度和MMA加料速度影响聚合速率和共聚物梯度结构,聚合温度升高和加料速度增大使聚合速率加快;改变单体与引发剂的配比,可以得到相应的相对分子质量聚合物。     

氯乙烯悬浮聚合过程引发体系优化

在氯乙烯悬浮聚合过程机理模型的基础上,建立了复合引发体系的优化模型,并进行了二元引发体系的优化研究,得到了不同引发剂配比下的最大聚合速率等高线和临界转化率时的聚合时间等高线。结果可以用来指导复合引发剂的配方设计,有助于聚合热的均匀释放、聚合釜冷却能力的充分利用和聚合釜生产率的提高。     

复合引发剂在氯乙烯悬浮聚合中的应用

(一)前言 在氯乙烯聚合中,设计有效的引发系统可以大大缩短聚合时间,提高聚合釜的能力,减少引发剂的使用量,提高产品质量,因此,国内外对氯乙烯聚合引发剂的开发和研制非常重视。     

乙烯基单体的預辐射聚合

电离輻射对于引发自由基机构的鏈式过程,特別是乙烯基单体的輻射聚合过程,是目前在化学上利用高能射綫最現实的方法之一。国外在这方面进行了大量的研究工作。約于1938～1940年开始研究的甲基丙烯酸甲酯和苯乙烯的輻射聚合,是研究得最早和最多的单体。輻射聚合与化学引发剂引发聚合相此較,具有許多独特的优点。如輻射聚合的引发速率与溫度无关,聚合过程可在低溫进行,其平均聚合度随溫度的升高而升高;高能射綫本身就是引发剂,可以制得高純度的聚合物;引发速率易于借輻射强度的調节而控制;輻射产生的自由基均匀地分布于整个系統,可以采用固相聚合等。研究表明,所有按自由基机构聚合的单体都能在高能射綫作用下聚合,在某种情况下,是唯一的方法。     

CO2和苯乙烯非平衡态等离子体连续引发聚合反应

利用自制等离子体引发聚合装置进行了ＣＯ２和苯乙烯（Ｓｔ）的等离子体连续引发聚合反应，并采用红外光谱、Ｘ射线光电子能谱和核磁共振谱对聚合产物的结构进行了表征。对比ＣＯ２／Ｓｔ等离子体引发聚合产物和常规方法聚合得到的聚苯乙烯的红外光谱图可以发现，前者在１...     

吗啡啉基-N-甲酸-丙烯酸乙二醇酯光聚合动力学的研究

采用实时红外技术对所合成的活性稀释剂吗啡啉基-N-甲酸-丙烯酸乙二醇酯的聚合动力学进行了测试。研究了光强和引发剂浓度对其光聚合的影响。结果表明随光强增加,聚合速率提高,当光强足够高时继续增加光强聚合速率反而会降低;当引发剂浓度升高时,聚合速率也越快,但当引发剂浓度足够高时继续增加引发剂浓度会使聚合速率下降。     

PVC树脂生产中引发剂选择

介绍了在氯乙烯悬浮聚合过程中,采用的合理有效的引发剂体系。实验及生产情况表明可以大大缩短聚合时间,提高聚合釜的生产能力,减少引发剂的使用量,提高产品质量。     

IPP一步合成就地引发聚合反应

一、前言 过氧化二碳酸二异丙脂(IPP)在氯乙烯聚合中是一种高效引发剂,它可以在较低温度下引发氯乙烯聚合,诱导期短,引发速度快,反应自始至终比较平稳,易于控制。加之原料易得,成本低廉,在国内外已得到广泛应用,是聚氯乙烯工业中最重要的引发剂之一。 IPP在聚合过程中的使用通常有两种方法,一种是将原料预先合成IPP,然后加入     

引发剂配方试验方法的研究与实践

本文在探讨反应放热峰的基础上，对氯乙烯悬浮聚合引发剂配方的试验方法进行了研究。笔者认为，通过小釜聚合实际，根据反应放热峰的等量关系原则可以寻求不同引发体系之间的用量关系，根据反应时间的等量关系原则可以寻求使用的一引发体系而大小不同釜的用量关系。     

过氧化苯甲酰引发剂存在下的反原子转移自由基聚合

在过氧化苯甲酰（ＢＰＯ）／ＣｕＢｒ２／ｂｐｙ（１∶２∶６）的存在下，首先使聚合体系在低温（６５℃）反应１０ｈ，然后再升高温度（１００℃）聚合，这样可以使甲基丙烯酸甲酯实现反原子转移自由基聚合。由于在反应中有ＢＰＯ和生成的亚铜离子的氧化还原反应，这种ＢＰＯ引发体系与ＡＩＢＮ存在下的反原子转移自由基聚合的引发机理不同。     

Porous graphitic carbon nitride synthesized via direct polymerization of urea for efficient sunlight-driven photocatalytic hydrogen production

Energy captured directly from sunlight provides an attractive approach towards fulfilling the need for green energy resources on the terawatt scale with minimal environmental impact. Collecting and storing solar energy into fuel through photocatalyzed water splitting to generate hydrogen in a cost-effective way is desirable. To achieve this goal, low cost and environmentally benign urea was used to synthesize the metal-free photocatalyst graphitic carbon nitride (g-C(3)N(4)). A porous structure is achieved via one-step polymerization of the single precursor. The porous structure with increased BET surface area and pore volume shows a much higher hydrogen production rate under simulated sunlight irradiation than thiourea-derived and dicyanamide-derived g-C(3)N(4). The presence of an oxygen atom is presumed to play a key role in adjusting the textural properties. Further improvement of the photocatalytic function can be expected with after-treatment due to its rich chemistry in functionalization.     

Photo-induced polymerization in ionic liquid medium: 1. Preparation of polyaniline nanoparticles

Photo-induced polymerization is employed to prepare polyaniline (PAN) nanoparticles in ionic liquid for the first time. Photons and photoactive ionic liquid cations replace conventional oxidants and metal complexes to promote the polymerization of aniline monomer. The diameter of the resulted PAN is confirmed in nano-scale by SEM. With increase of protonic acid in medium, the yield of the PAN increased, the UV absorption of the PAN strengthened, and a blue shift of the π-polaron absorption was observed. And the conductivity of the PAN also increased with the acid content in medium. The potential mechanism of photo-induced polymerization of aniline is proposed. Moreover, after the ionic liquid is separated from the reaction mixture and reused for five times, no obvious decrease in catalytic activity could be found in photo-induced polymerization of aniline. The method may open a new pathway to prepare nano-scale conducting polymers with sunlight.     

Synthesis and characterization of maleylated cellulose-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide hydrogel using TiO<Subscript>2</Subscript> nanoparticles under sunlight

Graft polymerization onto the cellulose is one way to produce semisynthetic copolymers and semiconductors were hardly used as initiators. Maleylated cellulose (MC) with different degree of carboxyl groups was synthesized and degree of carboxyl groups was determined using titration method. Then the graft copolymers of acrylamide (AM) on MC were synthesized by titanium dioxide semiconductor photoinitiator in aqueous suspension under sunlight. The effect of different parameters, such as the degree of carboxyl groups, degassing of atmosphere, reactor type, light source, MC/AM ratio, and initiator concentration, was evaluated in the synthesis of graft copolymers. MC with a high degree of carboxyl groups about 2.8 mmol g^?1 was selected for graft photopolymerization. Maximum monomer conversion (55%) for Maleylated cellulose-g-polyacrylamide (MC-g-PAM) was achieved with 0.5 mg TiO₂, MC/AM = 0.056, argon atmosphere, sunlight source, and double quartz tube reactor. The maximum amount of equilibrium swelling (41 g g^?1) was achieved for MC-g-PAM with 34% monomer conversion. The resulting graft copolymers were characterized by FT-IR, SEM, and TGA. Synthesis of MC-g-PAM using TiO₂ nanoparticles (NPs) as the initiator was done successfully that shows the TiO₂ NPs are useable in graft polymerization of acrylamide monomers onto the MC under sunlight.     

MXene-Based Soft Actuators with Multiresponse and Diverse Applications by a Simple Method

Smart actuators that can convert external energy stimuli into mechanical energy output have great potential in industrial, biomedical, and military applications. However, the existed disadvantage such as complex fabrication process, single stimulus source, and the requirement of artificial energy restrict their further development. Herein, a MXene/polyethylene (PE)-based soft actuator with multistimulus response and the ability to be driven by natural sunlight and human humidity is proposed through a simple method. Owing to the excellent electrical conductivity, high photothermal conversion capability, and surface hydrophilicity of MXene, the MXene/PE actuator exhibits rapid and large bending deformation in response to external multistimuli such as light, electricity, heat, and humidity. Owing to the simple preparation, and anisotropic, tailorable and programmable properties of the MXene/PE actuator, a soft robot that can crawl directionally under light conditions is constructed. In addition, based on the high sensitivity response of the actuator to light and humidity, smart clothing that can generate reversible bending deformation under natural sunlight as well as sweat conditions is developed. These results provide a new inspiration for the design of high-performance soft actuators with multistimulus response, and demonstrate the potential applications of the MXene/PE actuators in smart devices, bionic robots, and wearable clothing.     

聚苯乙烯与溶剂体系相容性的计算机模拟

使用推广的 Flory-Huggins理论结合 Monte Carlo法模拟聚苯乙烯与几种不同溶剂的相容性。用 Monte Carlo法从大量分子对中取样 ,计算配位数和相互作用能 ,将数据输入 Flory-Huggins格子模型中 ,估算出体系的混合自由能和相图 ,研究聚合度对聚苯乙烯与溶剂体系相容性的影响。模拟结果表明聚苯乙烯与甲苯等溶剂的相容性较好 ,与水等溶剂的相容性较差 ;随着聚苯乙烯聚合度增大 ,体系相容性变差 ;而且在聚合度较低时 ,相容性变差的程度更显著 ;以上结果与实际情况相符。     

New kinetic model for polymerization process of nylon 66 salt solution based on functional group non-isoactivity

The polymerization process of nylon 66 salt solution is a dynamically controlled process. Based on the assumption of unequal activity of functional carboxyl and amido groups, a new nylon 66 salt solution polymerization kinetic model was established by introducing the nylon salt dehydration reaction to the acid-catalyzed third-order reaction kinetic model and fitted to obtain the corresponding key kinetic parameters. The fitted salt dehydration reaction rate constant was 8.17×10^-3 kg?mol^-1?h^-1, while the activation energy was 19859 cal?mol^-1, respectively. Compared with Mallon model, the new developed model has a better fitting effect and can accurately predict the change of the polymerization process in a wider range of temperature and water content. Simulation results showed that salt dehydration reaction has an important effect on the polymerization process and the polymerization efficiency was relatively lower with higher concentration of nylon salt, especially under low temperature and high water content. Appropriately increase the reaction temperature or reduce the initial water content can accelerate the nylon salt dehydration reaction, thereby increasing the polymerization reaction efficiency. New nylon salt polymerization kinetics modeling method is not only applicable to nylon 66, but also to nylon 1212 and other salt solution polymerization systems.     

基于官能团非等活性假设的尼龙66盐溶液聚合动力学模型

尼龙66盐溶液聚合过程属于动力学控制过程。基于官能团非等活性假设，在Mallon酸催化3阶反应动力学模型基础上，引入尼龙盐脱水反应，建立了新的尼龙66盐溶液聚合反应动力学模型，拟合得到了关键反应动力学模型参数，其中盐脱水反应速率常数为8.17×10^-3 kg?mol^-1?h^-1、活化能为19859 cal?mol^-1。与Mallon模型相比，新模型拟合效果更优，可在更宽的温度和水含量范围内准确预测聚合过程的变化。模拟仿真发现，盐脱水反应对聚合过程有重要影响，低温和高水含量下尼龙盐浓度高，聚合效率低；适当提高反应温度或降低初始水含量可以加快尼龙盐脱水反应，从而提高聚合反应效率。新的尼龙盐聚合动力学建模方法不仅适用于尼龙66，也可应用于尼龙1212等盐溶液聚合体系。     

Comparison of the kinetics of conventional and microwave methyl methacrylate polymerization

A comparative investigation of the conventional and microwaves kinetics of methyl methacrylate (MMA) polymerization was performed. A method for determining the increase of the reaction rate in the microwave field (β) was presented. It was found that at all of the investigated temperatures and powers the polymerization rates increased in the presence of microwave energy by up to 8.9 times compared with conventional polymerization. Isothermal kinetics of the conventional MMA polymerization was investigated and its parameters were determined using isoconversion method. It was found that the calculated kinetics parameters changes complexly with degree of MMA conversion (α) and are in the mutual linear functional relationship, which is so called “compensation effect.” The complex changes of the kinetics parameters with α are explained with the postulated model for the mechanism of the MMA polymerization. The kinetics of the MMA polymerization under the microwave field (MWF) with different input power was investigated and its parameters were determined on the basis of the conversion‐temperature curves and Arrhenius equation. The values of the kinetics parameters for MMA polymerization in the MWF are dependent on α and are from 1.2 to 12 times lower than that for conventional MMA polymerization. A new method for the determination of activation energy (E_a) of the investigated process in the MWF was described. Decreased E_a value of the polymerization process in the MWF compared with the conventional polymerization is explained with the formation of the nonequilibrium energetic distribution of the reactants due to the rapid transfer of energy in the reaction system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1775–1782, 2007     

Analysis of the thermal stability and optical properties of KBiFe2O5 perovskite obtained by a polymeric precursor method

The solar cells are the most prominent devices to generate energy from sunlight, however, one of the main factors limiting the efficiency of photovoltaic conversion is the recombination of charge carriers in their active layer, which is generated by the inhomogeneity of the material that constitutes this layer. KBiFe₂O₅ is a perovskite with a high potential to be applied in the active layer of photovoltaic devices, however, it suffers from poor homogeneity during its synthesis, which is caused by the volatilization of K and Bi of its composition and, consequently, leads to the formation of secondary phases, which can sequester the charge carriers and decrease the efficiency of photovoltaic conversion. Thus, our objective is to evaluate the homogeneity of the powders obtained by the polymeric precursor method, its thermal stability until the formation of secondary phases, and the optical properties. With elemental mapping, it was possible to verify that the powder obtained was highly homogeneous and the band gap of 1.74 eV is within the optimal range for applications involving sunlight. Thus, it was possible to verify that this synthesis method generates highly homogeneous powders and at the temperatures employed does not undergo volatilization of K and Bi.     

New peracid-type polymeric initiator for radical polymerization

In this study, a radiation-induced copolymer, namely polyethylene-g-acrylic acid powder, was used, whose carboxyl groups can be oxidized to form a highly reactive polymer initiator. The activation energy for its decomposition is 22.4 kcal/mol. It was found that the peracid-type polymeric powder was effective as an initiator for radical polymerization. It had high reactivity toward 2-hydroxyethyl methacrylate (HEMA), which could be easily grafted onto the polymeric powder; also, the homopolymer could be obtained. The kinetic investigation indicated that this polymerization proceeded by a radial mechanism, and the overall activation energy of homopolymerization was 18.67 kcal/mol and the overall activation energy of bigraft polymerization was 17.35 kcal/mol. By using the peracid-type polymeric powder as initiator for the copolymerization of methyl methacrylate with styrene, it was confirmed that the polymerization initiated by the peracid-type polymeric powder was a radical reaction.