Selectively degradable alternating copolymers of isobutyl vinyl ether and plant‐derived aldehydes with acyclic side chains: Effects of side group structures on copolymerization behaviors

Side group structures of aldehydes were demonstrated to have decisive effects on cationic copolymerizations with alkyl vinyl ether (VE). Alternating copolymerizations of isobutyl VE (IBVE) and plant‐derived aldehydes with acyclic side chains such as trans‐2,cis‐6‐nonadienal, trans‐2‐nonenal, and citral proceeded under appropriate reaction conditions with the EtSO₃H/GaCl₃ initiating system. In addition, some aldehydes copolymerized in a well‐controlled fashion to yield alternating copolymers with controlled molecular weights and narrow molecular weight distributions. Quantitative and selective acid hydrolysis of the resulting alternating copolymers, based on the acetal structures in the main chains, was also achieved to give other conjugated aldehydes as nearly sole degradation products. Copolymerization results of IBVE and various plant‐derived aldehydes with acyclic or cyclic side groups suggested that electron‐donating ability and bulkiness of the side groups were most likely responsible for the alternating and/or controlled copolymerization behaviors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4684–4693     

A branch-and-price algorithm for the Vehicle Routing Problem with Deliveries,Selective Pickups and Time Windows

In the Vehicle Routing Problem with Deliveries, Selective Pickups and Time Windows, the set of customers is the union of delivery customers and pickup customers. A fleet of identical capacitated vehicles based at the depot must perform all deliveries and profitable pickups while respecting time windows. The objective is to minimize routing costs, minus the revenue associated with the pickups. Five variants of the problem are considered according to the order imposed on deliveries and pickups. An exact branch-and-price algorithm is developed for the problem. Computational results are reported for instances containing up to 100 customers.     

Biobased polyurethanes from polyether polyols obtained by ionic‐coordinative polymerization of epoxidized methyl oleate

A series of poly(ether urethane) networks were synthesized from polyether polyols obtained by ionic‐coordinative polymerization of epoxidized methyl oleate (EMO) using 4,4′‐methylenebis(phenyl isocyanate) or l ‐lysine diisocyanate as coupling agents. Moreover, a variety of segmented poly(ether urethane) networks with different hard segment contents were obtained using 1,3‐propanediol as the chain extender. The materials were characterized by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and tensile properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Unsaturated,biobased polyesters and their cross‐linking via radical copolymerization

Biobased, unsaturated polyesters derived from isosorbide, maleic anhydride, and succinic acid were synthesized and characterized. The presence of maleic anhydride units in the structure of the polyesters allowed converting them into cured coatings by radical copolymerization with crosslinking agents such as 2‐hydroxyethyl methacrylate, N‐vinyl‐2‐pyrrolidinone, acrylic acid or methacrylamide. The investigated polyesters were obtained via bulk polycondensation, catalyzed by titanium(IV) n‐butoxide. 2D NMR and MALDI‐Tof‐MS spectroscopy proved that this polymerization resulted in isomerization of maleic acid units into fumaric ones and in the formation of slightly branched structures by the reaction of isosorbide (end) groups with main chain unsaturated bonds. Moreover, some double bonds proved to have reacted with the condensation by‐product water. The resulting polyesters displayed the expected correlation between variables such as molecular weight and content of unsaturated bonds and their T_g values. Since the thermal properties of the obtained polyesters were appropriate for coating applications, the polymers were crosslinked with unsaturated monomers by radical copolymerization. The crosslinking process was studied using FTIR spectroscopy and by measurements of the soluble part of the cured coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2885–2895, 2010     

Combining renewable gum rosin and lignin: Towards hydrophobic polymer composites by controlled polymerization

Rosin polymer–grafted lignin composites were prepared via “grafting from” atom transfer radical polymerization (ATRP) with the aid of 2‐bromoisobutyryl ester‐modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated controlled and “living” characteristics of all monomer polymerizations. Thermal studies indicated that rosin polymer–grafted lignin composites exhibited glass transition temperatures in a broad temperature range from ～20 to 100°C. The grafting of both DA and rosin polymers significantly enhanced hydrophobicity of lignin. Static contact angle measurement of water droplets showed ～90° for all these rosin modified lignin composites. X‐ray photoelectron spectroscopy demonstrated that the surface of rosin–lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin‐modified lignin composites showed water uptake below 1.0 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Thieno[3,4‐b]pyrazine‐based low bandgap photovoltaic copolymers: Turning the properties by different aza‐heteroaromatic donors

A new series of low‐bandgap copolymers based on electron‐accepting thieno[3,4‐b]pyrazine (TPZ) and different electron‐donating aza‐heteroaromatic units, such as carbazole (CZ), dithieno[3,2‐b:2′,3′‐d]pyrrole (TPR) and dithieno[3,2‐b:2′,3′‐e]pyridine (TPY), have been synthesized by Suzuki or Stille coupling polymerization. The resulting copolymers were characterized by NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. UV–vis absorption and cyclic voltammetry measurements show that TPZ‐based copolymer with TPR has the best absorption due to the strongest intramolecular charge transfer effect and smallest bandgap. The basic electronic structure of D‐A model compounds of these copolymers were also studied by density functional theory (DFT) calculations. The conclusion of calculation agreed also well with the experimental results. The polymer solar cells (PSCs) based on these copolymers were fabricated with a typical structure of ITO/PEDOT:PSS/copolymer:PC₇₁BM/Ca/Al under the illumination of AM 1.5G, 100 mW cm^?2. The performance results showed that TPZ‐based copolymer with TPR donor segments showed highest efficiency of 1.55% due to enhanced short‐circuit current density. The present results indicate that good electronic, optical, and photovoltaic properties of TPZ‐based copolymers can be achieved by just fine‐tuning the structures of aza‐heteroaromatic donor segments for their application in PSCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polyterephthalates made from Ethylene glycol, 1,4‐cyclohexanedimethanol,and isosorbide

Three series of terephthalate polyesters (copolyesters and terpolyesters) containing 70, 80, and 90 mol % of ethylene glycol respectively, 1,4‐cyclohexanedimethanol (CHDM) and isosorbide in varying ratios, were synthesized by melt polycondensation. It was found that only ～75 mol % of the feeding isosorbide was incorporated in the resulting polyesters and that their content in diethylene glycol oscillated between 2 and 4 mol %. The polyesters had weight‐average molecular weights in the 25,000–33,000 g mol^?1 range and polydispersities between 2 and 2.5. The combined ¹H and ¹³C NMR analysis revealed that the microstructure of all these polyesters was at random. They showed good thermal stability with decomposition temperatures above 400 °C. Their glass‐transition temperatures were observed to increase with the content in cyclic diols, this effect being more pronounced when isosorbide was the replacing comonomer. Only the series containing 90 mol % of ethylene terephthalate units was able to crystallize upon cooling from the melt. Compared isothermal crystallizations revealed that isosorbide was more effective than CHDM in repressing the crystallizability of PET. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Novel suberin‐based biopolyesters: From synthesis to properties

This article reports the successful synthesis and characterization of two types of completely biobased polymers prepared by the polycondensation or polytransesterification of suberin fragments, isolated by different procedures and from two different vegetable sources. These polymerizations were conducted with different experimental conditions in terms of the type of catalyst, the reaction medium and temperature, as well as the molar ratio between the reactive moieties. The ensuing linear or partly crosslinked polyesters were characterized by conventional spectroscopic techniques, SEC, DSC, XRD, DMA, and TGA. These hydrophobic materials represent an original contribution to the growing field of polymers from renewable resources. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

高校人力资源管理中的模糊综合评判

人力资源管理是高校管理的重要组成部分。本简要介绍了高校人力资源的状况，讨论了模糊综合评判理论在人力资源管理中的应用。