Polyether polymer grafted modified nano-silica

(Polymer Research Institute, Department of Chemical Engineering, Tsinghua University, Beijing 1000084) With the development of polymer-based nanocomposites, surface modification of inorganic nanoparticles (such as silica, alumina, zinc oxide, calcium carbonate, etc.) More and more attention. It is an important chemical modification method that the polymer grafting and modifying the inorganic nano-particles to make the surface functionalized can effectively extract the dispersion and compatibility of the inorganic nano-particles in the polymer matrix material, thereby obtaining the mechanical properties. Excellent composite material. Because of their unique properties and diversified functions, polymer-modified inorganic nanoparticles can be widely used in other fields such as chromatographic separation, enzyme identification, and catalysis.

Polyethylene glycol is a common aliphatic linear polyether hydrazine molecule, which has good biocompatibility m, degradable and conductive properties, which makes it widely used in many fields. The Frechet polyether dendrimer is a new type of structural polymer that has been studied in recent years. It has a regular branched structure of aromatic polyethers. In this paper, it is reported that polyether-type polymers with different structures, polyethyl alcohol and Frechet polyether dendrimer, are grafted onto the surface of nano-silica by an isocyanate TDI coupling method. Similar studies reported generally use the two-step method to first react TDI with the inorganic powder and then use the isocyanate groups of the grafted TDI to react with the alcohol; or the first step is to use TDI to react with the alcohol to make its ends Functionalized as an isocyanate group and then used to graft inorganic nanoparticles. In this study, a simple and economical one-step method was successfully used to graft the nano-silicon oxide grafted with polyether polymer, and the mechanism of grafting reaction was discussed.

The basic idea of ​​the one-step method is to add the raw materials and reagents required for grafting into the reaction vessel at one time, and realize grafting through a one-step reaction process. Studies have shown that in the toluene solvent, 8 (TC without catalyst, TDI first and the oxidation 51:: reaction to form silica with isocyanate groups on the surface, and then these grafted isocyanate groups and poly The B-:alcohol (PEG) reaction achieves grafting, indicating that under the reaction conditions, the reactivity of silica with TDI is high and the reactivity of T PEG is TDI. At the same temperature and solvent, but the condition of adding catalyst DBTDL, K, is large. Part of the TDI first horse PEG reacted to form a trimer with isocyanate groups as end groups (the amount of TDI and PEG was 2:1). The dimer was reacted with the surface hydroxyl of the silica to achieve grafting, indicating the reaction conditions Underneath, PEG-related.It has been reported that in the synthesis of DBTDL-catalyzed polyesters, the transition state involves both isocyanates involved in intoxication.

When the reverse temperature is 80C, PEG is dissolved in the solvent, so it is easier to be activated, flashing and A is more humanly reactive. When the reaction was carried out at room temperature (20C), the presence of DBTDL could also achieve grafting, but the reactivity of oxyhydroxide and TDI was higher than that of PEG and TDI, which may be due to the fact that PEG was hard to dissolve butylbenzene at room temperature. Therefore, it is not easily activated. Frechet polyethers have lower reactivity than PEG. When the reaction temperature is 80 °C, the grafting rate is low under the condition of no catalyst, the grafting rate of the first generation polyether branches is only 2.9%; the grafting rate of the first generation polyether branches under the condition of catalyst DBTDL Up to 9.3%. It was observed in the study that although the molecular weights of the first-generation polyether dendrons and linear-stearyl alcohols are comparable, the former has higher reactivity than the latter, which indicates that the ether chain structure molecules are more than the pure carbon chain structure molecules Easy to graft.