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That is, the polymer is unstable in a water based environment. This is the prevailing mechanism for the polymers degradation. This occurs in two stages. 1. Water penetrates the bulk of the device, attacking the chemical bonds in the amorphous phase and converting long polymer chains into shorter water-soluble fragments.
Vinyl polymers are subject of several structural variations, which greatly expands the range of polymers and their applications. With the exception of polyethylene, vinyl polymers can arise from head-to-tail linking of monomers, head-to-head combined with tail-to-tail, or a mixture of those two patterns. Additionally the substituted carbon center in such polymers is stereogenic (a "chiral center")
The modification of surfaces to keep polymers biologically inert has found wide uses in biomedical applications such as cardiovascular stents and in many skeletal prostheses. Functionalizing polymer surfaces can inhibit protein adsorption, which may otherwise initiate cellular interrogation upon the implant, a predominant failure mode of ...
In the biomedical sciences, PVDF is used in immunoblotting as an artificial membrane (usually with 0.22 or 0.45-micrometre pore sizes), on which proteins are transferred using electricity (see western blotting). PVDF is resistant to solvents and, therefore, these membranes can be easily stripped and reused to look at other proteins.
Specific materials and their applications include polymer-protein and polymer-drug conjugates, mediation of enzyme activity, molecular recognition processes and polymeric micelles which can deliver a drug to a specific site in the body. [19] RAFT has also been used to graft polymer chains onto polymeric surfaces, for example, polymeric ...
The biodegradable polymers used in biomedical applications typically consist of hydrolyzable esters and hydrazones. These molecules, upon external stimulation, go on to be cleaved and broken down. The cleaving activation process can be achieved through use of an acidic environment, increasing the temperature, or by use of enzymes. [82]
An example of chain transfer in styrene polymerization. Here X = Cl and Y = CCl 3. In some chain-growth polymerizations there is also a chain transfer step, in which the growing polymer chain RM n ° takes an atom X from an inactive molecule XY, terminating the growth of the polymer chain: RM n ° + XY → RM n X + Y°.
There are vast examples and applications of biodegradable polymers. Bio-based packaging materials have been introduced as a green alternative in the past decades, among which, edible films have gained more attention due to their environmentally-friendly characteristics, vast variety and availability, non-toxicity, and low cost.