AFM investigation of polyolefines nanoobjects

A large variety of new states of polyolefines molecules such as polyethylene (PE) and ultra-high molecular weight polyethylene (UHMWPE), isotactic polypropylene (iPP), polybutene-1 (PB) were for the first time observed and characterized at nanometer scale by atomic force microscopy (AFM) and procedures of polymer deposition from diluted solutions at elevated temperatures. Common features of these states were selected and the classification was done in the following classes: unfolded or partially folded threads, condensates, nanofibers, nanocrystals and network structures. AFM images of unfolded threads indicate unexpectedly high chain rigidity of deposited molecules with a persistence length of the order of 5-10 nm in contrast to commonly accepted value of the order of 1 nm for flexible polymers such as polyolefines. AFM images of condensates reveal their high morphological similarity with the condensates of rigid DNA molecules. Monomolecular nanocrystallites were found to have most regular geometrical shapes and constant height step of 0.5 nm implying crystal type of chain packing. The observations on the whole indicate a surprisingly rich polymorphism of the states adopted by single polyolefines molecules or aggregates of few of them and require appropriate theoretical treatment.