Topological polymers — a new ICRI's research line
Polimery 1997, No 5, 306
The studies carried out at ICRI cover (1) topologically shaped oligomers and polymers and (2) compounds endowed with what is known as the topological bonds. Group one includes dendrimers and hyper-branched resins; group two includes rotaxane-structure compounds. The successive reactions of cyanoethylation of amines and cycloaddition of nitriles to cyanoguanidine allowed to prepare guanamine oligomers in four branching generations, endowed with characteristic dendrimer properties, v iz ., narrow molecular weight distribution and geometricaly progressing molecular weights in each successive generation. The fourth generation has a molecular weight of 3000 and shows the molecules to have experienced a considerable reduction of the hydrodynamic volume in the solution. The side reactions of the branching process include hydrolysis, which sometimes leads to the formation of lactams, and the retro Michael reaction. The alternating condensation (a kind of dendrimerization) was used to prepare hyperbranched phenolic and melamine-phenolic resins. For the latter, conditions were established to avoid the condensation of melamine's methylol groups with each other in favor of the condensation with phenol. Phenol uses one function only to yield multiphenols: bis-, tris-, tetrakis-, etc. Two products were obtained, having 5 or 3 phenol units on the average, combined with melamine through methylene bridges. The alternating condensation allowed to obtain stable colloidal resins and melamine-formaldehyde precondensates. Melting solid melamine resins of metallic luster were obtained in the same way. Among the topological-bonded polymers, vinyl polymerization products (polyrotaxanes) and dichlorodimethylsilane polycondensates in the presence of a- and cyanoethylated β-cyclodextrins were investigated.