Preparation And Characterization Of POSS Monomers And Their Utilization In Aqueous Polyurethane Dispersions

Polyhedral oligomeric silsesquioxane (POSS) is a cage-type inorganic/organic hybrid molecular. POSS has a well-defined, nano-scale structure and excellent compatibility. With molecular dimensions in the order of a single nanometer, POSS components not only bring the diversity but also make it easily compatible and well dispersed in organic polymers. Such nano-reinforced polymers significantly enhance the thermo-mechanical properties of materials while improving or retaining other physical properties, such as optical clarity, compatibility, and processability. Therefore, it is very significant to prepare POSS monomers and sduty its utilization in polymer materials.Water-based polyurethane (PU) with water as the dispersion medium, has some advantages such as no pollution, environmental protection, security etc., but it also brought many unfavorable factors such as lower strength, thermal properties, poor solvent and water resistance. In some areas, its application is limited due to the unsatisfactory performance. Utilizing POSS/PU hybrids is possibly a good approach for exploring the feasibility of new methods in improving these properties. POSS components not only bring the diversity but also make it easily compatible and well dispersed in polyurethanes, thus improving the thermo-mechanical properties, such as strength, heat resistance, water resistance, and modulus. However, the present POSS/PU hybrids are often limited to several POSS (mainly isobutyl-POSS) such that the more available POSS are rarely involved. Therefore, the preparation of novel POSS and new POSS/PU hybrids has good prospects for development.This paper describes the development, preparation methods of POSS and its utilization in aqueous polyurethane dispersions. The frame structure can be divided into three parts. The first part is an introduction and the second part is focused on the synthesis of POSS, both previously unknown species and known species. The third part is focused on its utilization in water-borned polyurethanes. The details as follows:Chapter1is the preface, which describes the origin, development and application of POSS. Most important, the current research of POSS was described and the preparation of many POSS compounds was summarized.Chapter2describes the preparation and characterization of incompletely condensed silsesquioxanes. Two important trisilanols (Trisilanolisobutyl POSS and Trisilanolphenyl POSS) were prepared with94-98%yield by a rapid, efficient and economical way though the base-catalyzed hydrolysis condensation. Moreover, the effect of synthesis conditions to the target product was also discussed and the synthesis conditions for trisilanols were optimized. Further, lithium hydroxide was chosen as catalyst to prepare trisilanols—the reaction conditions requires low, the operation conditions becomes simple and the difficulty for neutralization declines, thus becoming the better way to prepare trisilanols.Chapter3includes the preparation and characterization of functional POSS. A series of functional POSS (15POSS compounds), including novel single functional POSS and bridged amino POSS, were prepared by the hydrolysis condensation method and modified corner-capping method (feeding and assisted catalytic). What’s more, the structure of new functional POSS was characterized by IR, NMR, MS and XRD. Meanwhile, the impact of synthesis conditions to the target product was also discussed and the synthesis conditions were optimized. In preparing isobutyl POSS, Et4NOH or DBTDL was chosen as catalyst, with THF as the solvent, continuous reaction for18-24h below10℃, the yield of target product was satisfactory. While in preparing phenyl POSS, DBTDL was chosen as catalyst, with toluene as the solvent and silane was added dropwise to mixture below-8℃, the yield of target product was satisfactory.Chapter4describes the preparation and characterization novel phenyl-POSS/polyurethane aqueous dispersions and their hybrid coatings. The POSS/PU hybrid films are studied by Fourier transform infrared spectrometer (FT-IR), gel permeation chromatography (GPC), scanning electron microscope (SEM), X-ray diffraction (XRD) spectra, differential Scanning Calorimetry (DSC) analysis and thermal gravimetric analyzer (TGA). FT-IR and GPC are conducted to validate the chemical structure of the hybrid PU. The properties of hybrid films display significant changes with notable increases in glass transition temperature (Tg), thermal properties, tensile strength as well as surface hydrophobicity. These changes are attributed to the incorporation of novel POSS into PU. Moreover, these significant material property enhancements are achieved at low levels of POSS incorporation (only4%). Chapter5describes four novel HBPU/POSS hybrids were prepared by a straightforward step process and the influence about different POSS to the performance of hybrids. The resultant POSS/PU hybrid was found to be excellently super hydrophobic. The hybrids were demonstrated to increase Tg, thermal properties, modulus and mechanical strength. However, the degree of influence of different POSS to HBPU was much different. Isobutyl POSS increased the modulus and strength better than phenyl POSS, whereas phenyl POSS improved the thermal stability and Tg higher than isobutyl POSS.