Water-soluble polymers definitions

Cross-linked versions of water-soluble polymers swollen in aqueous media are broadly referred to as hydrogels (52) and have a growing commercial utility in such apphcations as oxygen-permeable soft contact lenses (qv) (53) (Table 4) and controUed-release pharmaceutical dmg deflvery devices (54). Cross-linked PVP and selected copolymers fit this definition and are of interest because of the following stmcture/performance characteristics ... 

RESINS (Synthetic). A manufactured high polymer resulting from a chemical reaction between two (or more) substances, usually with heat or a catalyst. This definition includes synthetic rubbers and silicones (elastomers), but excludes modified, water soluble polymers (often called resins). Distinction should be made between a synthetic resin and a plastic the formei is the polymer itself, whereas the latter is the polymer plus such additives as niters, colorant, plasticizers etc. See also Elastomers and Plasticizers. 

If the solvent of the coating solution does not wet the porous substrate, no pore penetration will occur. This method can be applied to coat porous hydrophobic polymers such as polyethylene, polypropylene, polytetrafluoroethylene or poiyvinylidene fluoride with a water soluble polymer. Since water does not wet the membrane (at least if the Laplace pressure is not e.xceeded) the polymer wB definitely not penetrate. The. solution properties are very important and this is determined by four parameters... 

There have been numerous definitions proposed for environmentally degradable and biodegradable water-soluble polymers and plastics, almost every article written on the subject includes the author s favorite definitions. All tend to encompass the same broad concepts but are slightly different in phraseology depending on the author s perspective... 

To use organic molecules as a food source, microorganisms have to be able to take up the substance and metabolize it within their cells. A prerequisite is that the molecules are water-soluble and that they are small enough to pass through the cell walls and membranes of the microorganism. Polymers are typically not water-soluble and, by definition, are not small molecules [4]. Therefore, the biodegradation of polymers typically needs to follow four distinct steps. 

A new class of water soluble cellulosic polymers currently receiving attention Is characterized by structures with hydrophobic moieties. Such polymers exhibit definite surface activity at alr-llquld and liquid-liquid Interfaces. By virtue of their hydrophobic groups, they also exhibit Interesting association characteristics In solution. In this paper, results are presented on the solution and Interfaclal properties of a cationic cellulosic polymer with hydrophobic groups and Its Interactions with conventional surfactants are discussed. 

An emulsion polymerization requires the mechanism of polymer particle nudeation to reside outside the monomer droplets. This physical-chemical process involves a series of radical reactions in the continuous phase followed by homogeneous or micellar particle formation. Either of these mechanisms require the initiator to be insoluble in the monomer phase, such as a water soluble initiator and an organically soluble monomer, or vice versa. If, in contrast, the initiator is soluble in the monomer phase, all the components of the reaction are contained in the dispersed phase and the continuous phase serves only to decrease the viscosity and dissipate heat Such polymerizations are categorized as suspensions. The second definition, however, makes no statement as to the magnitude of n and therefore the two criteria are mutually exclusive. 

Polymers which meet the definition of a polymer of low concern are eligible for the new Synthetic Polymers of Low Concern Category. A synthetic polymer of low concern is one which has a Mn >10(X), low charge density, low residual monomer content, does not dissociate readily, has low water solubility, if solid has a particle-size distribution such that <1% of particles have a diameter of <70 pm, is stable under conditions of use, and does not contain reactive functional groups. For these polymers less information is required and applications will be processed within 50 d. 

---