Synthesis and Characterization of Segmented Polyurethanes Containing Polyhedral Oligomeric Silsesquioxanes Nanostructured Molecules

Abstract

Segmented polyurethanes based on diphenylmethane-4,4 -diisocyanate and polytetramethylene glycol were synthesized using a mixture of polyhedral oligomeric silsesquioxane (POSS)-diol and 1,4-butanediol as chain extenders. The polymers were characterized by differential scanning calorimetry, wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS) and tensile property tests. Microphase separation between the hard and soft segment domains was observed in all the samples by SAXS. The increase of the POSS concentration was found to weaken the microphase separation between the domains and increase the T g of the soft segments. The WAXD results showed that when the POSS concentration was greater than 10 wt%, the 101 diffraction peak from the POSS crystals could be observed, which suggested the formation of POSS nanocrystals in the hard domain. The tensile property tests showed that polyurethanes containing the nanostructured POSS molecules had higher moduli, but lower maximum elongation ratios.

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

“…The POSS molecules have been successfully incorporated into many polymers, such as styryls, acrylics, liquid-crystalline polyesters, siloxanes, and polyamides. [22][23][24][25][26][27][28][29][30][31] Either by chemical or physical means, the POSS molecules can be dispersed in the polymer matrix by the adjustment of the chemical groups attached to the silicon atoms. The addition of POSS molecules can enhance many properties, such as heat resistance, oxygen permeation, and hardness.…”

The influence of POSS nanoparticles on selected thermal properties of polyurethane-based hybrids

“…In this case, functionalized POSS, usually containing one or more OH groups participate in the reaction and form urethane bonds with diisocyanates leading to often complex architectures which we are going to describe in the following. The reaction may take place in the presence of small amounts of a suitable solvent such as tetrahydrofuran (THF) [30], N,N-dimethylformamide (DMF) [31], methyl ethyl ketone (MEK) [32], dimethylacetamide (DMAC) The influence of POSS nanoparticles on selected thermal properties of polyurethane-based hybrids 291 [33] or even in solvent-free environments [34,35] in which case the polyol dissolves the other components (diisocyanate and POSS). The selection of the solvent is obviously crucial for the effective reaction and good dispersion of the POSS moieties.…”

Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes

“…Crystal size of the copolymers in the 101 direction can be estimated by the Scherrer formula (equation 11) analyzing the most intense reflection at 2θ=7.2° L = (k λ)/(β hkl cosθ) (11) where β hkl is the half-height width of the hkl indexed reflection, θ = diffraction angle, λ = wavelength of radiation source, and k is a constant close to unity. Results concerning high POSS level powders are reported in Table 5 for both copolymer series.…”

“…For example, it has been reported that introduction of POSS in an inherently amorphous architecture, like a methacrylic random copolymer, completely suppresses its crystallization behaviour [8]. By contrast, in other cases, ordered, self-assembled hybrid structures were found in polystyrene [9], polynorbornene [10], polyurethanes [11], polybutadiene [12] and even when host matrices were crystallizable like in case of polyethylene [13,14]. The nature of the obtained nanostructure, whether amorphous or crystalline, has a significant effect also on physical properties of the hybrid material like its stiffness or thermal stability.…”