Polyether block-copolymer surfactants

Extensively studied nonionic surfactants are PDMS / polyether block copolymers [31] and poly(ethylene oxide) substituted trisiloxanes [32-35]. They are able to achieve a maximum surface tension depression to about 21 mN/m and a low critical micelle concentration (CMC) [36], These siloxane surfactants can self-assemble into a variety of... 

The DLVO theory does not explain either the stability of water-in-oil emulsions or the stability of oil-in-water emulsions stabilized by adsorbed non-ionic surfactants and polymers where the electrical contributions are often of secondary importance. In these, steric and hydrational forces, which arise from the loss of entropy when adsorbed polymer layers or hydrated chains of non-ionic polyether surfactant intermingle on close approach of two similar droplets, are more important (Fig. 4B). In emulsions stabilized by polyether surfactants, these interactions assume importance at very close distances of approach and are influenced markedly by temperature and degree of hydration of the polyoxyethylene chains. With block copolymers of the ethylene oxide-propylene oxide... 

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

The nonionic derivatives are primarily represented by the polyether-polydimethyl-siloxane copolymers. The general structure of these surfactants is illustrated below. The hydrophilic chain(s) generally contain EO/PO block copolymers. When several hydrophilic chains are distributed on the polymer backbone, the resulting molecular structure is similar to a comb therefore, such molecules are often called comb-like surfactants. 

Amphiphilic polymers, mainly block copolymers, may self-assembly in aqueous medium rendering structures similar to micelles of conventional surfactants (polymeric micelles) or vesicles that resemble liposomes (polymersomes). The hydro-phobic regions of the polymer chains form the core, while the hydrophilic blocks extend towards the aqueous phase as a shell. The resultant polymeric micelles can host drugs of diverse polarity in the core or in the core-shell interface, enhancing the apparent solubility of the drug up to several orders of magnitude [36], A variety of amphiphilic polymers have been synthetized. Common examples of hydrophilic blocks are poly(ethylene oxide) (PEO), poly(N-vinyl pyrrolidone), poly(N-isopropylacrylamide) or poly(acrylic acid) (PAA). Suitable hydrophobic blocks may be PLA, PCL, poly(propylene oxide) (PPO), poly(trimethylene carbonate), polyethers, polypeptides, and poly(P-aminoester)s [37-39]. 

Chem. Descrip. Polysiloxane-polyether copolymer surfactant Uses Foam stabilizer for mfg. of rigid PU foams, continuously laminated PU board-stock, pour-in-place foams, rigid block foams Properties Cl. vise, liq. dens. 1.055 0.01 g/cc vise. 450 120 mPa-s solid, pt. < -15 C hyd. no. 120 12 cloud pt. 64 3C (4% aq.) pH 6.5 1.5 (4% aq.)... 

All types of conventional non-ionic surfactants have at one time or another been recommended for use in polyester and, in certain instances, in polyether polyurethanes. However, the predominant surfactants used today are the silicones. These materials are block or graft copolymers or polydimethyl siloxanes and polyalkylene oxides. The polyether part is usually a copolymer of propylene and ethylene oxides. Variations in the commercially available surfactants are in the molecular weight and the weight ratio of the two blocks, the ratio of ethylene oxide to propylene oxide in the polyether portion, and the type of link between the silicone and... 

---