Polymaleamide–polymaleimide networks

Polymaleamide–polymaleimide networks were obtained as films by the thermal treatment of mixtures with different ratios of an aliphatic–aromatic polymaleamide (PMA) and 4,4′‐bis(maleimidodiphenylmethane) (BMI), in N‐methyl‐2‐pyrolidinone (NMP) as a solvent. The polymaleamides were synthesized by ring‐opening polyaddition of 1,6‐hexamethylene–bisisomaleimide with 4,4′‐diaminodiphenylmethane in NMP at room temperature. The networks are infusible and insoluble in organic solvents; therefore, they were studied by solid‐state techniques such as IR, DSC, thermooptical analysis (TOA), TG/DTG analysis, and TEM. Thermal treatment of pure PMA and BMI occurs with the formation of crosslinked structures as proved by IR spectra. DSC and TOA curves show the appearance of chemical interactions between PMA and BMI in cured films and the formation of ordered morphologies, especially when BMI is the major component. TG/DTG and TEM results supported these observations. The PMA–polymaleimide network films present electrical insulator properties superior to individual polyamides or polyimides. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 779–788, 2004     

Synthesis of telechelic polyacrylates with unsaturated end-groups

A convenient, one-pot synthesis of telechelic and semi-telechelic polyacrylates with unsaturated end-groups has been developed. Atom transfer radical polymerization of methyl or n-butyl acrylate was initiated with either ethyl α-bromomethylacrylate or methyl dichloroacetate, as a monofunctional or difunctional initiator, respectively, and mediated with various Cu/amine complexes. Addition of excess ethyl 2-bromomethylacrylate was found to not only immediately quench the polymerization but also installed 2-carbethoxyallyl moieties on the ends of the polymer chains. The telechelic polymers were found to undergo thermally or photochemically induced crosslinking reactions.     

Role of end-groups and catalyst in polyester cyclodepolymerization and cycle-chain equilibria

The influence of polyesters end-groups on cyclic oligoester formation is investigated using a series of hydroxy-, carboxy- and methylester-terminated aliphatic polyesters, in the presence of various ester interchange catalysts. The presence of hydroxy end-groups is the preponderant factor on cyclodepolymerization kinetics. This indicates that the main reaction is the intramolecular hydroxy–ester interchange reaction between hydroxy end-groups and ester functions in the chain. Carboxy-ester and ester–ester interchanges play a minor role, as the cycle-chain equilibrium is reached only very slowly when carboxy- or ester-terminated polyesters are reacted. High temperature and the presence of tin catalysts are also favorable factors, while, as expected, dilution shifts the equilibrium toward the formation of high yields of cyclic oligoesters. A mechanism is proposed, based on the reverse of the “coordination-insertion” mechanism established for the ring-opening polymerization of lactones.     

NMR based determination of minute acid functionality: end-groups in PET

Conditions are determined for the carbodiimide-mediated room temperature esterification of the carboxylic acid end-groups of poly(ethylene terephthalate) with hexafluoroisopropanol. The hexafluoroisopropyl ester is quantified with ¹⁹F NMR, using α,α,α-trifluorotoluene as a secondary standard. This provides a technique for accurate determination of minute amounts of carboxylic acid functionality in small samples of polymers, and potentially in animal and plant based foods.     

Synthesis of conjugated polyphenylacetylenes with redox active ferrocenyl end-groups

Summary Metathesis polymerization has been employed for the synthesis of polyphenylacetylene (PPA) containing redox-active ferrocene groups at both ends. Two reversible one electron oxidation waves were detected in CV. The ΔE values decreased with increase in chain length of the polymer, indicating that the metal-metal interaction decreases by increasing the chain length. Received: 19 March 1999/Revised version: 7 May 1999/Accepted: 11 May 1999     

Advances in RAFT polymerization: the synthesis of polymers with defined end-groups

This paper provides an overview and discusses some recent developments in radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). Guidelines for the selection of RAFT agents are presented. The utility of the RAFT process is then illustrated with several examples of the synthesis of polymers with reactive end-groups. Thus, RAFT polymerization with appropriately designed trithiocarbonate RAFT agents is successfully applied to the synthesis of narrow polydispersity carboxy-functional poly(methyl methacrylate) and primary amino-functional polystyrene. Methods for removing the thiocarbonylthio end-group by aminolysis, reduction and thermal elimination are discussed. It is shown that the thiocarbonylthio end-group can be cleanly cleaved by radical induced reduction with tri-n-butylstannane, to leave a saturated chain end, or by thermolysis, to leave an unsaturated chain end.     

Novel polymaleimide containing dibenzoyl hydrazine pendant group as chelating agent for antimicrobial activity

Novel polymaleimide containing dibenzoyl hydrazine pendant group, poly[N-benzoyl-4-(N-maleimido)-phenyl hydrazide], and its metal complexes have been synthesized. Their antimicrobial activity against Bacillus subtilis, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Escherichia coli bacteria and that against Aspergillus fumigatus, Syncephalastrum racemosum, Geotrichum candidum, and Candida albicans fungi were investigated. The polymer–metal complexes showed better antimicrobial activity than that of the parent polymer. The inhibition of the growth of the microbes remarkably depends on the type of the metal in the complexes. The polymer–Co(II) and the polymer–Cd(II) complexes are more potent in inhibition of the tested microbes growth than the rest of the prepared complexes.     

A novel feed‐stock recyclable hyperbranched polymaleimide: Synthesis and characterization

Hyperbranched polymaleimide can be readily obtained by copolymerization of allyl maleimide and propyl maleimide. A hyperbranched polymaleimide was obtained in a yield of 56 wt % in 3 h at 50°C, whose weight average molecular mass and polydispersity index were measured by size‐exclusion chromatography to be 59,000 and 4.1, respectively. TGA showed a one‐step mass loss process in the decomposition of the hyperbranched polymaleimide. The dominant pyrolysis mechanism was revealed by gas chromatography/mass spectrometry to be depolymerization. The major pyrolysates of the hyperbranched polymaleimide were allyl maleimide, propyl succinimide, and other volatile monomeric units. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1848–1852, 2006     

A novel method for determination of polyester end-groups by NMR spectroscopy

An efficient, convenient and quantitative method for characterising polyester end-groups is described. We have found that trichloroacetyl isocyanate (TAI) reacts rapidly and quantitatively with both carboxyl [C(O)OH] and hydroxyl (OH) chain ends to form derivatives that can be readily determined by ¹H NMR spectroscopy. The TAI capped end-groups give rise to characteristic imidic NH resonances in a normally clear region of the ¹H NMR spectrum [δ∼10-11.5 for C(O)-O-C(O)-NH-C(O)CCl₃ from C(O)OH, δ∼8-9 for O-C(O)-NH-C(O)CCl₃ from OH]. The method has been successfully applied to quantitative determination of the end-groups of a wide variety of oligomeric polyesters. It has also been applied to higher molecular weight polyesters including commercial, bottle grade, poly(ethylene terephthalate) (PET) and PET based copolyesters (e.g. PETG).     

Photopolymerization of butyl acrylate-in-water microemulsions: Polymer molecular weight and end-groups

Solubilization of butyl acrylate in water using sodium dodecyl sulfate (SDS) and 1-pentanol produced transparent oil-in-water microemulsions stable at room temperature. These microemulsions were polymerized using a two-component water-soluble initiator system comprising of Rose Bengal (RB) and methyldiethanolamine (MDEA). These compounds undergo photo-induced electron transfer upon absorption of visible light to produce amine radicals active in free radical polymerization. Analysis of the NMR spectra of polymers revealed only monomer peaks and amine fragments which were incorporated as the polymer ends. Effect of initiator composition on polymer length was also investigated using GPC. When RB concentration was increased with constant concentration of excess MDEA, the average chain length decreased up to a specific concentration where after the polymer length reached an asymptotic value. Experiments were performed to identify this asymptotic value and it was observed that as the MDEA concentration was increased, the asymptotic values of number average degree of polymerization decreased.     

多马来酰亚胺改性聚苯醚树脂的热分解动力学研究

采用热重分析法对自制的3,3′-二乙基-4,4′-二苯甲烷型多马来酰亚胺(PEDM)改性烯丙基化聚苯醚(PPO)固化树脂的热分解动力学进行了研究。结果表明:在热作用下,共聚交联体系在PPO的苯氧醚键处首先断链,并按无规断链或自由基引发断链方式迅速进行,交联网络被破坏成许多线形分子链,但其他键受影响很小,热分解表现为一级反应,且失重速率很快;随温度升高,当体系的苯氧醚键基本上断裂完毕后,线形分子链上的马来酰亚胺环的羰基或其他能量相近的键也开始逐渐断裂,此时热分解也表现为一级反应,但速率比第1步慢得多。     

离子液体的制备及N-烷基化反应研究

简述了离子液体的制备及在离子液体中进行的N.烷基化反应,比较传统合成方法,有时间短、产率高、污染小、易操作等优点.     

Amphiphilic telechelics with polyhedral oligosilsesquioxane (POSS) end-groups: Dilute solution viscometry

Using capillary viscometry, we have investigated the associative behavior of new amphiphilic telechelics incorporating polyhedral oligosilsesquioxane (POSS) as an end-group of poly(ethylene glycol) (PEG) chains of varying length. Solution viscosities were strongly affected by the solvent composition in THF/water mixtures. When water, a selective solvent for PEO segments but a selective non-solvent for POSS segments, was added to the THF solutions, behavior common to polyelectrolytes was observed. In particular, for relatively high concentrations the reduced viscosity remained nearly concentration-invariant for both POSS telechelics and pure PEG homopolymers, indicating a limiting molecular weight of aggregates. On the other hand, a dramatic increase in the reduced viscosity was observed with decreasing concentration for lower concentration values, suggesting aggregate formation and a concentration-dependent aggregate size.     

Ionic liquids in separations

Ionic liquids are liquids composed completely of ions. In the past two decades, ionic liquids have been widely used as "green solvents" replacing traditional organic solvents for organic synthesis and catalysis. In addition, ionic liquids are playing an increasingly important role in separation science. In this Account, the application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.     

离子液体中氧化反应研究进展

离子液体用作氧化反应的溶剂,已经显示了许多潜在的优点。该文对在不同离子液体中进行氧化反应的类型、催化剂种类、达到的效果进行了评述,指出了存在的问题和发展方向。引用文献34篇。