Reversible polymer modification

By adding only about ten additional statements to this program, a program for simulating reversible polymer modification and epimerization reactions was derived. Use of CSMP to generate plotted output and to evaluate kinetic parameters are also illustrated. 

TITLE REVERSIBLE POLYMER MODIFICATION REACTIONS / CALL ERRSET(209,100,=1,1)... 

These results also demonstrate that the template based polymer modification can be quite fruitful strategy and can lead to libraries of materials for commodity applications as well as for various sophisticated functions. Currently, we are studying comparative catalysis not only to improve the new functional group compatibility but also to explore reversal of regionselectivities and efficiencies. 

Woghiren C, Sharma B, Stein S (1993). Protected thiol-polyethylene glycol a new activated polymer for reversible protein modification. Bioconjug. Chem. 4 314-318. 

Like dynamic polymers in general, those of covalent type present specific properties that non-reversible polymers do not possess. They have been illustrated for instance in degradable green polymers based on imine connections [72], in polymer blending [73], in the modification of mechanical [74] and optical [75] properties. Metallosupramolecular polymers are also able to undergo dynamic modification of their mechanical and optical properties, as shown in Fig. 5 [53-55]. 

Fig. 9 Thermoresponsive dynamers. Top Generation of an amphiphilic poly(acyUiydrazone). Bottom Inverse thermal response to heat stimulation, with thermally induced, reversible size modification through large and reversible polymer growth in response to an increase in temperature...

H. Mehdizadeh, J. M. Dickson. Theoretical modifications of the finely porous model for reverse osmosis. J Appl Polym Sci 42 1143, 1991. 

Most ester-forming reactions are reversible. Depending on circumstances, these reactions may be either undesirable side reactions, for example hydrolytic chain scissions occurring during processing, or useful reactions when chemical modification or polymer recycling is considered. 

Reverse-phase HPLC (RP-HPLC) separates proteins on the basis of differences in their surface hydophobicity. The stationary phase in the HPLC column normally consists of silica or a polymeric support to which hydrophobic arms (usually alkyl chains, such as butyl, octyl or octadecyl groups) have been attached. Reverse-phase systems have proven themselves to be a particularly powerful analytical technique, capable of separating very similar molecules displaying only minor differences in hydrophobicity. In some instances a single amino acid substitution or the removal of a single amino acid from the end of a polypeptide chain can be detected by RP-HPLC. In most instances, modifications such as deamidation will also cause peak shifts. Such systems, therefore, may be used to detect impurities, be they related or unrelated to the protein product. RP-HPLC finds extensive application in, for example, the analysis of insulin preparations. Modified forms, or insulin polymers, are easily distinguishable from native insulin on reverse-phase columns. 

Ilhan F, Gray M, Rotello VM. Reversible side chain modification through noncovalent interactions. Plug and play polymers. Macromolecules 2001 34 2597-2601. 

Hawker et al. 2001 Hawker and Wooley 2005). Recent developments in living radical polymerization allow the preparation of structurally well-defined block copolymers with low polydispersity. These polymerization methods include atom transfer free radical polymerization (Coessens et al. 2001), nitroxide-mediated polymerization (Hawker et al. 2001), and reversible addition fragmentation chain transfer polymerization (Chiefari et al. 1998). In addition to their ease of use, these approaches are generally more tolerant of various functionalities than anionic polymerization. However, direct polymerization of functional monomers is still problematic because of changes in the polymerization parameters upon monomer modification. As an alternative, functionalities can be incorporated into well-defined polymer backbones after polymerization by coupling a side chain modifier with tethered reactive sites (Shenhar et al. 2004 Carroll et al. 2005 Malkoch et al. 2005). The modification step requires a clean (i.e., free from side products) and quantitative reaction so that each site has the desired chemical structures. Otherwise it affords poor reproducibility of performance between different batches. 

---