A complete force field (MSXX) for simulation of all nylon polymers is derived from ab initio quantum calculations. Special emphasis is given to the accuracy of the hydrogen bond potential for the amide unit and the torsional potential between the peptide and alkane fragments. The MSXX force field was used to predict the structures, moduli, and detailed geometries of all nine nylons for which there are experimental crystal data plus one other. For nylon-(2n) with 2n ≤ 6, the α crystal structure (with all-trans CH2 chains nearly coplanar with the hydrogen bonding plane) is more stable, while for 2n > 6, γ (with the alkane plane twisted by 70°) is more stable. This change results from the increased importance of methylene packing interactions over H bonds for larger 2n. We find the highest Young's modulus for nylon-7.

Polymeric biomaterials, especially agricultural commodity-based polymers, have been moving forward quickly during the last few years because of the significant rise in oil and natural gas prices. From a life-cycle perspective, sugar is a renewable resource that has the potential to be used as an alternative to petroleum-based polymers. The objective of this work is to demonstrate the wide utility of a cereal-derived material, isosorbide, for high added value applications in polymers. As a bicyclic ether derivative of glucose, isosorbide is classified by the Food and Drug Administration as a ''generally recognized as safe'' (GRAS) material. Because of its rigidity, chirality, and nontoxicity, isosorbide can be incorporated into thermosets and thermoplastics. Such processes and products offer a more sustainable and ''green'' technology. By making the diglycidyl ether, isosorbide epoxy resins were synthesized in this work as a new class of thermosets with comparable dry mechanical property similar to bisphenol A (BPA) epoxide. These could be a potential replacement for BPA in coatings and adhesives. By controlling the stereochemistry, multiple isosorbide-derived AB monomers such as isosorbide methyl terephthalate were synthesized for future homopolymerization and copolymerizations with commercial available polymers like polyethylene terephthalate (PET) and PLLA. The increased glass transition temperature and semicrystalline morphology of these isosorbide copolyesters demonstrate a way to improve the performance of polyester thermoplastics in many applications such as hot-fill containers and engineering resins. All the intermediates generated during the syntheses were characterized by NMR. The thermal tests were conducted using the techniques of DSC and thermogravimetric analysis (TGA). Figure 2. NMR of isosorbide diglycidyl ether. Scheme 3. Synthetic route of bisisosorbide diglycidyl ether.

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When melt‐extruded in the presence of triphenylphosphite (TPP), the molecular weight of polyesters such as poly(ethylene terephthalate) (PET) increases with time. Analysis of the PET chain end groups and model studies of high‐temperature reactions indicate that, most likely, the process leading to chain extension of PET in the presence of TPP takes place in two steps. In the first step, TPP rapidly reacts with the hydroxyl end groups by displacing one phenoxy group from the TPP. In the second step, a slow reaction takes place between the alkyldiphenyl phosphite and carboxylic chain end groups, forming an ester bond between the carboxyl and alkyl groups, and producing diphenylphosphite (DPP) as a reaction by‐product. The DPP tautomerizes to its pentacovalently bonded stabler form of diphenylphosphate, the form in which the DPP was usually detected in our analyses. The ester formation results in the extension of the PET chains. Model studies are presented which support the proposed mechanism.