Characterization of the polymer of a dipyrrolyl monomer by pyrolysis mass spectrometry

In this work, characterization of a homopolymer of succinic acid bis(4‐pyrrol‐1‐ylphenyl) ester prepared by galvonastatic polymerization was carried out by direct pyrolysis mass spectrometry. Although decomposition of the monomer yielding mainly butadionic acid and pyrrole occurred under the galvonastatic polymerization conditions, growth of the polymer through the pyrrole moieties was also achieved, yielding a ladder‐type polymer film. The polypyrrole chains contained both quinoid and aromatic units as in the case of polypyrrole, yet the extent of network structure was significantly diminished. A three‐step mechanism is proposed for the thermal decomposition process. The first step involves the cleavage of C₄H₄NC₆H₄O end groups. In the second step, decomposition of phenyl ester units and polypyrrole chains having quinoid structure takes place. The final stage of thermal degradation was attributed to decomposition of polypyrrole chains having aromatic structure. Copyright © 2004 Society of Chemical Industry     

Radical homopolymerization and copolymerizations of ring-methoxy substituted α-cyanostyrenes

Radical homopolymerization and copolymerizations of ring-methoxy substituted α-cyanostyrenes were studied using benzoyl peroxide and dimethyl 2,2′-azobisisobutylate at 60°C. It was found that the cyanostyrenes containing 2-methoxy cyanostyrene gave homopolymer in moderate yield and they were also copolymerized with vinyl monomers such as styrene and vinyl acetate. The relative reactivity of the cyanostyrenes towards a polystyryl radical (1/r₂) in the copolymerization of cyanostyrenes (M₁) and styrene (M₂) was correlated with the Hammett and Taft substituent constants of the methoxy groups and the ¹³C NMR chemical shift of the β-carbon of the cyanostyrenes. The enhancement of the radical polymerization reactivity by introducing a nitrile group in the captodative α-position of styrene was considered to be due to the suppression of the termination reaction and the activation of the propagation reaction. In addition, thermal properties such as glass transition and degradation temperatures of the cyanostyrene polymers obtained were also examined.     

Thermoreversible hydrogels. XV. Swelling behaviors and drug release for thermoreversible hydrogels containing silane monomers

Three series of thermosensitive copolymeric hydrogels were prepared from [3‐(methacryloyloxy)propyl]trimethoxysilane (MPTMOS), [2‐(methacryloyloxy)ethoxy]trimethylsilane (METMS), and (methacryloyloxy)trimethylsilane (MTMS), referred to as the silane monomer, and N‐isopropylacrylamide (NIPAAm) by solution polymerization. The influence of the structures and amounts of silane monomers on the swelling and drug‐released behaviors were studied. The results showed that, because of the hydrophobicity of the silyl group, the more silane monomers in the copolymeric hydrogels the lower was the swelling ratio of the gels. The hydrophobicity of the silyl group affected the swelling mechanism, which resulted from the non‐Fickian diffusion for the gels. The copolymeric gels clearly exhibited gel transition temperatures. The copolymeric hydrogels could be applied to a drug‐release and drug‐delivery system. The delivery amount would approach a steady state after three cycle operations of delivery. The gels also showed an on–off switch behavior on drug release depending on the temperature, and the gels released more CV with the gels in a swollen state. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2523–2532, 2002     

Structural and mechanistic aspects of the thermal degradation of poly(vinyl chloride)

A critical review of the title subject supports the following major conclusions. Thermal dehydrochlorination of poly(vinyl chloride) (PVC) begins with internal allylic chloride and tertiary chloride structural defects formed during polymerization. The tertiary chloride is associated with 2,4-dichloro-n-butyl, 1,3-di(2-chloroethyl), and chlorinated long branches. Mechanisms for the formation of all of the labile defects are well established. ‘Carbonylallyl’ structures and certain isotactic conformers of ordinary monomer units are unimportant as initiators of thermal dehydrochlorination. Both the initiation and the subsequent formation of conjugated polyene sequences occur via carbenium chloride ion pairs or by a closely related concerted four-center quasi-ionic route. Six-center concerted processes, pathways involving free radicals, and other mechanistic schemes suggested recently are not involved in polyene elongation. However, during thermal degradation, ordinary monomer units are converted into internal allylic chloride defects by a mechanism that may include the abstraction of hydrogen by triplet cation diradicals derived from polyene intermediates. Cyclization reactions seem likely to contribute to the termination of polyene growth. When PVC is thermolyzed in blends with other polymers, unusual kinetic phenomena are detected that remain to be fully explained.     

Particle nucleation in emulsion copolymerization containing multifunctional monomers

Characteristic features of particle nucleation and growth in the emulsion copolymerization of styrene and multifunctional monomers such as ethylene glycol dimethacrylate and divinylbenzene were investigated. It was found that in these emulsion copolymerization systems the rate of polymerization per particle decreased drastically with an increase in the content of the multifunctional monomer in the initial monomer feed, and the number of polymer particles produced, on the other hand, increased corresponding to the decrease in the rate of polymerization per particle. The increase in the number of polymer particles produced was explained on the basis of Smith-Ewart theory, which predicts that the number of polymer particles produced would increase inversely proportional to the 0.4 power of the volumetric growth rate per particle, that is the rate of polymerization per particle during the interval of particle formation (Interval I). It was pointed out that the decrease in the rate of polymerization per particle in Interval I would be due mainly to a decrease in the monomer concentration in the polymer particles which was caused by crosslinking networks of the resultant polymer.     

三甲基烯丙基氯化铵－丙烯酰胺共聚物的合成与结构表征

报道了三甲基烯丙基氟化铵（ＴＭ）的制备及其与丙烯酰胺的共聚。对ＴＭ的合成条件进行了探讨，对引发体系、温度，单体配比对共聚反应的影响进行了研究，并用ＩＲ、ＮＭＲ、差热分析及化学分析方法对其结构进行了表征。     

Fabricating Tunable Superhydrophobic Surfaces Enabled by Surface-Initiated Emulsion Polymerization in Water

Fabricating controllable superhydrophobic surfaces remains challenging in various fields ranging from chemical industries to biomedical engineering. Conventional methods commonly require volatile organic solvents and the assistance of special surface deposition and modification equipment, which are detrimental to environment and limit their applications in micro-devices. Herein, an equipment-free method is reported to directly transform fluorinated monomer micro-droplets into hydrophobic polymer particles on flat substrate surfaces in water, simultaneously depositing hydrophobic coatings with tunable surface structures. The as-prepared surfaces show superior superhydrophobicity and great stability in extreme conditions (e.g., varying acidity, basicity, and heating conditions), and excellent anti-fouling property. Meanwhile, surface hydrophobicity can be manipulated by adjusting emulsion droplet number density and reaction time. Hence, superhydrophobic surfaces with tunable hydrophobicity gradients have been successfully fabricated in one pot. This study provides an equipment-free method to facilely fabricate controllable superhydrophobic surfaces, with great potential in the development of smart superhydrophobic materials in various engineering and industrial applications.     

Fluorinated Black Phosphorene Nanosheets with Robust Ambient Stability for Efficient and Stable Perovskite Solar Cells

Extraordinary electronic and photonic features (e.g., tunable direct bandgap, high ambipolar carrier mobility) render few-layer black phosphorus (BP) nanosheets/quantum dots an important optoelectronic material. However, most of the BP applied in metal halide perovskite solar cells (PSCs) are produced by sonication-assisted liquid exfoliation, which inevitably brings inferior electronic properties, thus leading to limited beneficial effects. Furthermore, this study uncovers that the intrinsic instability of BP nanosheets sandwiched between (CsFAMA)Pb(BrI)₃ perovskite and spiro-OMeTAD has a deleterious effect on the performance stabilization of PSCs. To address the above constraints, a feasible strategy herein is developed by introducing high-quality fluorinated BP (F-BP) nanosheets synthesized by one-step electrochemical delamination. In addition to P-Pb coordination, there is a strong hydrogen bond between F^? and MA⁺/FA⁺ as well as an ionic bond between F^? and Pb²⁺ for the perovskite/F-BP interface, thus leading to fewer interfacial traps than perovskite/BP, which is responsible for the highest power conversion efficiency (22.06%) of F-BP devices. More importantly, F-BP devices exhibit significantly improved humidity and shelf-life stabilities due to the excellent ambient stability of F-BP, resulting from the antioxidation and antihydration behavior of fluorine adatoms. Overall, the findings provide a promising strategy to simultaneously enhance the photovoltaic performance and long-term stability of BP-based PSCs.     

苯乙烯/羟甲基丙烯酰胺无皂乳液共聚合的研究

以苯乙烯为主单体,N-羟甲基丙烯酰胺为功能性单体、K2S2O8为引发剂制备了固含量较高、稳定性较好的苯乙烯/N-羟甲基丙烯酰胺无皂共聚物乳液,探讨了固含量、单体配比、反应温度、引发剂用量等条件对乳液稳定性和粒径大小的影响。结果表明,合成最佳条件为固含量25%,功能性单体20%,引发剂1.7%,反应温度75℃。     

常温固化含氟聚氨酯涂料的研究进展

含氟聚氯酯涂料兼备了舍氟树脂及聚氯酯的优异性能而表现出超强的耐候性、耐久性、耐化学性、耐腐蚀性、耐沾污性等特性。介绍了常温固化含氟聚氨酯涂料的研究进展。