Polyurethane-POSS hybrid materials: by solution blending and in-situ polymerization processes

Polyhedral oligomeric silsesquioxane (POSS) is a nanostructured softmaterial that tremendously influences the properties of polymers. This paper delineates the preparation of polyurethane-POSS hybrid materials by physical blending and in-situ polymerization, and studies their properties. In the physical blending method, a polyurethane (BDO-PU) was prepared by using polycaprolactone diol (PCL-diol) as a soft segment, 4,4'-methylenebis(phenyl isocyanate) (MDI) as a diisocyanate and 1,4-butanediol (BDO) as a chain extender. The PU-POSS hybrid material (BDO-PU/POSS) was then prepared by the dispersion of POSS (octahydroxy POSS) molecules in the synthesized BDO-PU matrix by the solution mixing method. In the in-situ polymerization method, POSS-PU and POSS-BDO-PU hybrid materials were prepared using POSS and the combination of POSS andBDOas a crosslinker or a chain extender. The formation of PU and PU-POSS hybrid materials was confirmed by Fourier transform infrared and differential scanning calorimetry analyses. The introduction of octahydroxy POSS molecules into the PU matrix resulted in a reduction of glass transition temperature (T-g). However, POSS-PU hybrid materials prepared by the in-situ polymerization method had significantly less T-g compared to the hybrid materials prepared by the solution or physical blending method. The incorporation of POSS molecules by using the in-situ polymerization process resulted in an increase in the surface hydrophobicity (water contact angle, WCA = 125.) compared to the same prepared by using the solution blending process (WCA = 106.). Moreover, the WCA values of all hybrid materials (WCA = 106-125.) are much higher than those of the pristine BDO-PU (WCA = 84.). The higher WCA value of the hybrid materials is due to the combined effect of the hydrophobic nature of POSS molecules as well as the increased surface roughness, as evidenced by the AFM 3D images. The hybrid materials prepared by the in-situ polymerization method exhibited improved mechanical and thermal properties compared to those prepared by the solution blending method.