Hydrolytic susceptibility

The hydrolytic susceptibility of the fluoromethylene cyanate ester is greater than that of the aromatic cyanate ester. Direct contact with water results in measurable hydrolysis to the carbamate in a 24-h period for the former while the latter is unaffected.9... 

To our knowledge, there has so far been no comprehensive comparison of the wide array of available coupling procedures leading to gem-diaminoalkyl derivatives. However, due to the hydrolytic susceptibility of gem-diaminoalkyl derivatives (Scheme 6),I% fast coupling methods seem to be advantageous. 

Polymers, (II) and (III), containing hydrolytically susceptible segments at a physiological pH between 6.5 and 7.5 were previously prepared by the author [2] and used as viscoelastic liquids containing gel microparticles. 

Hubbell [2] prepared biocompatible hydrogels consisting of poly(acrylic acid-b-ethylene oxide) crosslinked with hydrolytically susceptible carbonates, (IV), urethanes, (V), ureas, (VI), ester amides, (VII), and diamides, (VIII). 

The versatile coordination mode of oxoligands, which can bind up to six metal centers, is the main reason for the formation of cyclooligometallic derivatives. Although hydrolytic susceptibility decreases with increase in the number of oxoligands, even then the complex remains moisture-sensitive, perhaps due to the incomplete coordination sphere of the metal. These oligomeric complexes may take several weeks to crystallize at low temperature. Upon controlled hydrolysis, the polymeric [Sn(ONeoPent)2]co molecule yields products (11) and (12)." ... 

IR spectroscopy may be used to follow two reactions occurring in polyimides exposed to high temperatures and humidities hydrolysis of the imide linkages and hydrolysis of residual anhydride end groups. The hydrolytic susceptibilities of several polyimides were measured at 90°C/95% R.H. Polymers based on benzophenone tetracarboxylic acid dianhydride (with either oxydianiline or m-phenylene diamine) appeared to undergo rather rapid hydrolysis initially, but the reaction had essentially halted by the time the measured imide content had decreased by 5-6%. Polymers based on 3,3 ,4,4 -biphenyl tetracarboxylic acid dianhydride (with p-phenylene diamine) and pyromellitic dianhydride (with oxydianiline) showed no significant imide hydrolysis. In all the polymers, the anhydride was hydrolyzed quite readily. 

The results given above indicate that, despite some variations in rate, anhydride end groups can all be classed as quite readily hydrolyzed. In contrast, the hydrolytic susceptibility of imide linkages varies much more with the polymer examined. BPDA-PDA showed no measurable imide hydrolysis whatsoever. In PMDA-ODA the amount of hydrolysis observed was small enough that we cannot eliminate the possibility that impurities in the anhydride component, rather than PMDA itself, resulted in the formation of hydrolyzable material. Of the polymers studied here, only those that contained BTDA as the anhydride component showed a marked susceptibility to imide hydrolysis. Even in this case, the data suggest that the reaction is limited in that only about 6-7% of the imide linkages appear to be susceptible to hydrolysis. 

The reason for this pattern is not yet clear. As seen in the data presented in Table III, there is no strong correlation between the final cure temperature and the degree of hydrolysis after long-term exposure. Similarly, films of different thicknesses do not show significant differences in the amount of imide eventually hydrolyzed, suggesting that hydrolytic susceptibility is not related to surface effects. One possibility still under consideration is that different conformations of the benzophenone moieties result in different hydrolytic susceptibilities. 

Functionality of the precursor (number of the OR groups) Increase in metal coordination number Hydrolytic susceptibility OR > OAc > 6-dik... 

It is of particular interest that PBS has a higher hydrolytic degradation rate than poly(butylene succinate-co-butylene adipate) (PBSA) copolymers, as shown in Fig. 17 (Ahn et al. 2001). It is suggested that the presence of butylene adipate units may promote the hydrophobic nature of copolyesters, which would negatively influence the hydrolytic susceptibility by sterically hindering the access of nucleophiles. 

Thomas, D.B., et al. 2004. Hydrolytic susceptibility of dithioester chain transfer agents and implieations in aqueous RAFT polymerizations. Macromolecules 37(5) 1735-1741. 

In yet another approach Katsarava et al, s)mthesized regular PEAs based on natural amino acids (Arabuli, 1994). Their choice of an a-amino acid to introduce hydrolytic susceptibility was based on the fact that the esters of N-acyl-L-a-amino acids are easily cleaved by Q -chymotrypsin and at a rate five orders in magnitude... 

Over-stabilization is a temptation, in order to ensure long shelf lives for cyanoacrylate adhesive. This practice should be avoided because it leads to sluggish cure rates and inferior bond strengths. The use of strong protic acids can lead to hydrolysis of the cyanoacrylate ester group, producing alcohol which will destabilize the adhesive as its concentration increases. Because of the hydrolytic susceptibility of cyanoacrylate monomers, the water content of these adhesives should be kept as low as possible. Over-stabilization with strong acids should also be avoided in order to minimize hydrolysis. 

Degradable polyurethanes designed with hydrolytically susceptible soft segments... 

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