Reactive Polymers最新文献

A method of characterization of the protonation equilibrium of ethylenediamine (EDA) in a cation-exchange membrane is propounded. This method involves an intermediate reaction of the membrane (initially in the mixed EDAH⁺EDAH₂²⁺ form) with gaseous carbon dioxide then the elution and the titration of the carbamic acid formed. This method is more precise and is preferred to the conversion of the sorbed EDAH⁺ and EDAH₂²⁺ into EDA by sodium hydroxide followed by an acidic titration. The selected method allows to calculate accurately the apparent equilibrium constant K^∗ of the protonation of EDA in the membrane and is very useful to characterize the carrier (EDAH⁺) content of membranes conditioned to achieve facilitated transport of carbon dioxide. The data obtained will be used in an improved analysis of this transport process.

The synthesis of several coordinating polymers by grafting thiourea functional groups onto commercial macroporous polystyrene polymer matrices are described. In this paper, we also report the study on the absorption and elution of precious metal ions (or together with base metal ions, Cu²⁺ and Fe³⁺) from acidic chloride solutions. The results showed that these resins have appreciable capacity and good selectivity for the absorption of gold from acidic solutions. The extraction kinetics of the resins is slower than the corresponding monomolecular ‘free’ extractant analogues. However, some of the resins show acceptable extraction rates.

Dynamic contact angle analysis with Wilhelmy's plate technique was found to be useful for characterizing the chemical interactions that occur on conducting polymers. The derivatized pyrroles, 3-carboxy-4-methylpyrrole and 3-carbethoxy-4-methylpyrrole, along with pyrrole, were used to prepare polymers with a range of polarities. The predicted trend of polarity, based upon the chemical structures of the polymers, was verified with the technique. It has also been shown that the substrate employed during electropolymerization process plays a major role in determining the properties of the resultant polymer.

Derivatives of protected phenols with chiral aminoalcohol or aminoether-containing substituents in the 4-position of the aromatic ring were prepared and shown to react readily, after deprotection, with chloromethylated styrene-divinylbenzene polymers. The chirality in the substituents originated either from the use of a chiral monomeric aminoalcohol derivative or from the introduction of a chiral epoxide, which in turn was ring opened by a chiral amine. The chiral epoxides were obtained by either asymmetric synthesis or starting from a chiral glycidyl derivative.

The strongly hydrogen bonded complexes of polyvinylphenol and tetra-alkylammonium fluorides show unusual and unexpected thermal behaviour consistent with the in situ alkylation of the polymer.

Polymer-supported chiral Lewis acids were prepared from bromoboranes and crosslinked polymers having chiral amino alcohol or diol moieties. These polymers were used as chiral catalysts for Diels-Alder reactions of cyclopentadiene with methacrolein to give optically active cycloadduct in high chemical yield with high exo selectivity. Optical yield up to 54% ee was obtained by the use of polymeric chiral catalyst derived from (S)-proline. The potential of this type of approach in asymmetric synthesis is discussed.