Comparison of Small Molecule and Polymeric Urethanes, Thiourethanes, and Dithiourethanes: Hydrogen Bonding and Thermal, Physical, and Mechanical Properties

Abstract

The hydrogen bonding behavior of a homologous series of small molecule and polymeric urethanes, thiourethanes, and dithiourethanes was investigated in solution, melt, and solid states. The relative hydrogen bonding strengths in both small molecule and polymer systems were evaluated, and the results were compared to theoretical calculations of hydrogen bonding strength. The results for NMR and FTIR analysis of the small molecule models indicated that the NH protons on the carbamate and thiocarbamates have greater hydrogen bonding strengths than the NH protons of the dithiocarbamate. The polyurethane and polythiourethanes were found to have approximately equivalent physical and mechanical properties as a result of a similar extent of hydrogen bonding, whereas the polydithiourethane, due to a lower degree of hydrogen bonding, has reduced thermal and mechanical transition temperatures as well as lower hardness values. The polythiourethane and polydithiourethane networks exhibit narrower glass transitions compared to polyurethane networks, apparently the result of an efficient isocyanate/isothiocyanate-thiol reaction with little or no side products. Because of weakness of the C-S bond compared to the C-O bond, thiourethanes and dithiourethanes have lower thermal stability than the corresponding urethanes. Finally, the polythiourethanes and polydithiourethane have higher refractive index values than their polyurethane counterpart.

Characterization of methacrylate-based composites containing thio-urethane oligomers

“…The use of thio-urethanes in the polymer coatings and molded parts industry has been widely reported [33,36]. Those networks have demonstrated the capacity of improving mechanical properties, more specifically toughness, due to a more homogeneous polymer network formation in comparison to simple urethane counterparts [36].…”

“…Those networks have demonstrated the capacity of improving mechanical properties, more specifically toughness, due to a more homogeneous polymer network formation in comparison to simple urethane counterparts [36]. Recently, work by our group has demonstrated that this technology can be translated into dental materials applications through the relatively simple approach of including pre-polymerized thio-urethane oligomers into the methacrylate matrix [25,26].…”

Inverting Polyurethanes Synthesis: Effects on Nano/Micro-Structure and Mechanical Properties

“…Hydrogen bonding distribution and micro/nano-phase segregation behavior of polyurethanes as function of their precursors chemistry, physical properties or synthesis procedure are important factors when predicting chemical and physical characteristics of potential new materials (3,(9)(10)(11). While typically, talking or writing about STPUEs morphology, it has been referred to as "polyurethanes microstructure," it should be pointed that the incompatibility between hard segments (HS) and soft segments (SS) lead to a nanoescale phase separation with hard nano-domain ranging between 5-20 nm size (3,(12)(13)(14)(15), which truly trend to assemble into 3D spherulite-like microstructures (14).…”

New thermoplastic poly(thiourethane-urethane) elastomers based on hexane-1,6-diyl diisocyanate (HDI)

“…Poly(thiourethane)s, poly(thioester)s and poly(thiocarbonate)s have been synthesized and investigated mainly as potential plastics with high thermal and chemical resistance, as well as with high refractive index for optical applications (i.e., lenses and optical fibers) [1,[4][5][6][7].…”