AASERT: Microphase Separation, Viscoelastic Properties and Aging of Amorphous Polyurethane Elastomers

摘要

Thermally stable polynrethanes with low flow temperatures were synthesized at fixed soft segment content (50%), and the relationship between their microstructure and linear viscoelastic properties were studied as a function of block length and block incompatibility. It was found that the materials changed from homogeneous to microphase-separated as segment length and incompatibility increased. Dynamic mechanical experiments demonstrated that unlike most di-and triblock copolymers, polyurethanes are incapable of developing long-range order due to large polydispersity in their segment length. A separate part of this report involves synthesizing novel biocidal dendrimers by converting the end groups of poly(propylene imine) dendrimers to quaternary ammonium salts. The antibacterial properties of these dendritic biocides against Escherichia coli were evaluated using a bioluminescence method. Bioluminescence studies showed that novel dendritic architecture improved the potency of quaternary ammonium compounds over 100 times against E. coli. The activity of these biocidal dendrimers against Staphylococcus aureus was characterized by suspension tests. The effectiveness of these series of dendritic biocides depended on the length of alkyl chains used in the quaternization and dendrimer size (generations). Biocides from PPI dendrimers were also shown to be more effective than those derived from Perstop hyperbranched polymers.