Polyether-polysiloxane block copolymer

Multiple emulsions of the oil-in-water-in-oil type, where both the inner and the external oil phases were medium chain triglyceride (MCT), were prepared by the two-step emulsification method. The emulsifying agent at the inner oil-water interface was a combination of WPI-xanthan gum hybrid at different ratios and 3wt% Abil EM90 (a hydrophobic polyether-polysiloxane block copolymer) as the external emulsiher. Typical multiple emulsion composition is described in Table 7.2 and release profiles of flumethrin (a veterinary drug model) at 25°C are presented in Figure 7.15. 

Polyether-polyester polyol hybrids, 25 472 Polyetherimide-polysiloxane block copolymers, 24 698, 704, 708... 

Carbanions can react with Cl in PVC macromolecules [295] and with the ester group of PMMA [284]. The rates of the two reactions are probably not very different by the addition of a-methylstyrene tetramer dianion to a PVC + PMMA solution, the copolymer poly(vinyl chloride)-gro/ir-poly-(methyl methacrylate) was obtained [296]. Macrocations formed by the reaction of strong acids with polyalkenes (see Chap. 3, Sect. 3.2) react with polyethers (polysiloxanes) yielding graft and block copolymers, e. g. poly(propylene)-0ra/ir-poly (oxyethylene) [297], poly(propylene)- /ocA -... 

O Neill and coworkers approached the problem of CO2 solubility from a different perspective, taking low cohesive energy density (and hence weak self-interactions) to be the key parameter (38). Solubility studies on diverse polymers such as polyethers, polyacrylates, polysiloxanes, and many block copolymers demonstrated that a decrease in the cohesive energy density... 

Block copolymers, formed by transesterification of blend components or otherwise, will act as interfacial agents in blends of immiscible polymers which are identical to or compatible with the components of the block copolymer. A recent patent application for a system of this type refers to the use of triblock copolymers of polymer A-polysiloxane-polymer B as interfacial agents in blends of polymers A and B which have different polarity or hydrophilicity [6]. In this case the intermediate polysiloxane blocks, strongly immiscible with either polymer A or polymer B, helps to drive the copolymer to the A-B interface and reduce the possibility of dissolution of the copolymer in either blend phase. In the example quoted polymer B is PCL (or a non-polar polyether) and polymer A is a polar polyether or other polar polymer. 

Silicones are polymers with backbones consisting of—[Si(R>2—O]— repeating units. They are prepared by reacting chlorosilanes with water to form silanols that condense to form siloxanes. Silicone oils made from dimethyldichlorosilane and methyltrichlorosilane are used as additives to reduce surface tension. Chemically modified silicone fluids, such as polysiloxane/polyether block copolymers, with broader ranges of compatibility have been described (175). 

Another synthetic strategy is the transformation of ring-opening polymerization to controlled radical polymerization. The transformation of the active site from one to the other can be performed in the polymerization system or after separation and purification. The active sites can be obtained by reacting functionalized polymer with appropriate reagents. Various block copolymers containing polyether (or polyester, or polysiloxane or polyacetal) blocks and vinyl polymer blocks have been prepared by this method. 

Chem. Descrip. Polysiloxane-polyether block copolymer Uses Foam stabilizer and emulsifier for rigid PU and polyisocyanurate foams with max. demand on flow properties esp. for refrigeration and pipe insulation Properties Cl, vise, liq, sol. in common rigid foam polyols and resin preblends dens. 1,055 0,01 g/cc vise. 750 170 mPa-s solid, pt. < -8 C hyd. no. 100 10 cloud pt. 70 3 C (4% aq.) pH 6.5 1.5 (4% aq.)... 

Chem. Descrip. Polysiloxane-polyoxyalkylene block copolymer Uses Foam stabilizer for hot-cured polyether PU foams Features Low emanation... 

---