The effect of diisocyanate isomer composition on properties and morphology of polyurethanes based on 4,4′-dicyclohexyl methane diisocyanate and mixed macrodiols (PDMS-PHMO)

Abstract

Three series of polyurethanes were prepared having 42 wt % hard segments based on 4,4Ј-dicyclohexyl methane diisocyanate (H 12 MDI) with trans,trans isomer contents in the 13 to 95 mol % range and 1,4-butanediol chain extender. The soft segments were based on macrodiols poly(hexamethylene oxide) (PHMO, MW 696), ␣,-bishydroxyethoxypropyl polydimethylsiloxane (PDMS, MW 940), and two mixed macrodiol compositions consisting of 80 and 20% (w/w) PDMS. H 12 MDI with 35, 85, and 95% trans,trans isomer contents were obtained from commercial H 12 MDI (13% trans, trans) by fractional crystallization, and all polyurethanes were prepared by a one-step bulk polymerization procedure. The polyurethanes based on the commercial diisocyanate-produced materials soluble in DMF with molecular weights in the 53,655-75,300 range and generally yielded clear and transparent materials. The polyurethanes based on H 12 MDI with trans,trans contents of 35% or higher yielded materials insoluble in N,N-dimethylformamide (DMF) and were generally opaque. Mechanical properties, such as tensile strength and elongation at break, decreased with increasing trans,trans content, while the Young's modulus and Shore hardness increased. The polyurethanes based on mixed macrodiols yielded higher tensile properties than those of materials based on individual macrodiols. The best mechanical properties were observed for a polyurethane consisting of a soft segment based on PDMS-PHMO (80/20) and a hard segment based on commercial H 12 MDI and BDO. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the polyurethane morphology. DSC results confirmed that the polyurethanes based on H 12 MDI with high trans,trans isomer were very highly phase separated, exhibiting characteristic hard segment melting endotherms as high as 255°C. The other materials were generally phase mixed. FTIR spectroscopy results corroborated DSC results.

Influence of Hard Segment Content and Diisocyanate Structure on the Transparency and Mechanical Properties of Poly(dimethylsiloxane)-Based Urea Elastomers for Biomedical Applications

“…Hence, the effects of the diisocyanate structure and symmetry on the morphology and tensile properties of PUs, polyurethaneureas, and PUrs has been addressed in various studies. For example, Adhikari et al and Saralegi et al both studied the influence of the symmetric trans - trans -4,4′-methylenebis(cyclohexyl isocyanate) (H 12 MDI) isomer ratio on the mechanical properties and microphase separation of PUs [ 23 , 24 ]. They found that microphase separation in the PUs increases due to a higher HS ordering.…”

Preparation and Properties of Polydimethylsiloxane (PDMS)/Polyethylene Glycol (PEG)-Based Amphiphilic Polyurethane Elastomers

“…These characteristics include but are not limited to the very low T g (−123 °C), good thermal and oxidative stability, satisfactory release properties, and excellent electrical insulation properties. , Jasna Djonlagić et al found that polyurethanes containing ethoxypropyl-poly­(dimethylsiloxane) macrodiol exhibited an excellent resistance to the fibrinogen adsorption and showed more favorable adsorption for albumin than that for fibrinogen in the competitive adsorption assay, suggesting their good hemocompatibility. However, the incompatibility of the nonpolar PDMS segments between hard segments resulted in a PUE with poor mechanical properties, such as low elongation. ,, Raju Adhikari et al found that the elongation at the break of the polyurethanes containing PDMS was about 310%. Many efforts have been made to synthesize PDMS-based polyurethanes with good mechanical properties, with the primary focus on the enhancement of the interfacial adhesion between the soft domains and the hard domains. , These techniques include mixing with polar oligomeric polyols (polyether or polyester), the introduction of polar groups to PDMS, and hard segment modifications.…”

Synthesis and properties of waterborne poly(urethane urea)s containing polydimethylsiloxane

“…These properties include an extremely low glass‐transition temperature ( T g ; −123°C), low surface tension, high flexibility, high permeability to gases, chemical inactivity, insulating stability, very good thermal stability, and UV stability 10–13. In the past, many studies were published in which PDMS was used as a component of PU to improve PU properties such as water resistance, flame resistance, and heat resistance 14–16. However, few studies on PDMS‐modified WBPUs and UV‐curable WBPUs have been reported recently 17…”

“…[10][11][12][13] In the past, many studies were published in which PDMS was used as a component of PU to improve PU properties such as water resistance, flame resistance, and heat resistance. [14][15][16] However, few studies on PDMSmodified WBPUs and UV-curable WBPUs have been reported recently. 17 Shape-memory polymers (SMPs) are capable of changing their shape on exposure to a stimulus such as heat, electrical current, or photoenergy.…”