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Poly(ester amide)s (PEAs) composed of variable diols, dicarboxylic acids, and α-amino acids were synthesized and characterized to elucidate structure–property relationships. The PEAs were synthesized using both solution and interfacial approaches to obtain varying molecular weights (MWs) and polydispersities. Studies using differential scanning calorimetry and powder X-ray diffraction revealed a range of amorphous and semicrystalline behavior that was dependent on structure. The viscosities of the PEAs as a function of temperature were studied by rheology, and phase transitions were confirmed for some polymers. Mechanical properties were also investigated, and it was found that the PEAs could be tuned to exhibit elastomeric or brittle behavior by varying both the length of the diol and the amino acid moiety. This information provides new insights into the effects of PEA structure, MW, and MW distribution on PEA properties and will aid in the design and selection of PEAs with optimal properties for targeted applications.

This paper documents and discusses the field validation of a simple performance indicator for specification grading of asphalt cement for thermal cracking. The loss tangent, tan(δ), as defined by the ratio of the viscous over elastic modulus, G”/ G’, is able to provide a quantitative measure of the sol and gel nature of asphalt cement. As such, tan(δ) relates closely to how well a material is able to relax stress and is therefore investigated as a surrogate performance indicator for thermal cracking. Asphalt cements from 20 contract sites in Ontario, Canada, were tested in torsion bar geometry to determine their viscoelastic properties. The findings show that tan(δ) was able to distinguish good from poor performers for this set of materials with 95% accuracy, which is a considerable improvement over the current bending beam rheometer protocol. In addition to the use of tan(δ), it is suggested that a measure of the critical strain tolerance in the ductile state could be included to provide a significantly improved performance grading method. Most of the worst performing contracts were found to contain zinc. The presence of this element suggests that the use of waste engine oils in asphalt production is likely widespread, since zinc is a universal additive in engine oil and is never found in straight asphalt cement

A photodegradable poly(ester amide) was developed. An amphiphilic graft copolymer derivative with paclitaxel conjugated via ester linkages formed micelles that released paclitaxel in response to UV light.