LOW ENERGY PATHS AND REORIENTATION OF SIDE-GROUPS OF POLYMERS DURING CONFORMATIONAL STATE TRANSITION

INTRODUCTION The conformational state transition of polymer chains relates to crystallization processes, migration ofthe chains in solution, fluctuation of the end-to-end distance of random coils, and the relaxation and phasetransitions of polymers. A description of the conformational state transition requires questions about; 1) howmany stable conformational states for a specific σ bond; 2) the barriers between the states; 3) the mechanismof the conformational transition; 4) any cooperative behavior during the transition. Flory and his coworkers

A RHEOLOGICAL MODEL FOR POLYMER MELTS WITH INTERNAL STRUCTURE IN FLOW FIELDS

Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.

Role of Conformational Entropy in Complex Macromolecular Systems

Conformation is the key to revealing the physical characteristics of macromolecular systems and receives tremendous interest from the fields of polymer physics and biological materials.The conformational entropy,related to the number of conformations of the macromolecule,plays a predominant role in the structural formation,transition,and dynamics of macromolecular systems.In this review,we present a comprehensive overview of the research,development and applications of the conformational entropy in complex macromolecular systems.We begin by discussing the physical origin of the conformational entropy based on statistical mechanics of macromolecules in classical polymer physics,and then introduce the recent progress on the predictive modeling of the conformational entropy,associated with a variety of typical macromolecular systems.Furthermore,we also highlight several principles and rules,which have been harnessed to manipulate the structural organization of complex macromolecular systems through the conformational entropy.We anticipate that this review will further promote fundamental research in polymer physics,and offer intriguing prospects for applications in complex macromolecular systems including biomacromolecules,grafted nanoparticles,and polymer nanocomposites.

POSS-modified PEG Adhesives for Wound Closure

PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth. The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility. Compared with the sutured wounds, the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig, demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.