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In this feature article, we first make some simple reviews about the most popular theories for glass transition: 1) Free volume theory, 2) Entropy theory, 3) Götze’s Mode coupling theory, and 4) Caging and Jamming theory. We address the issue of existing studies of glass transformations. Then, we review some special colloidal/polymer model systems which can give a repulsive potential together with...
Crystallization behaviors of crystalline–crystalline diblock copolymers are important in understanding the structure evaluation. In this work, we investigated effects of crystallization temperature on the interactive crystallization behavior of crystalline–crystalline diblock copolymer of poly(l-lactide)-block-poly(ethylene glycol) copolymer (PLLA-b-PEG) with differential scanning calorimetry (DSC),...
The present work deals with the flow-induced multiple orientations and crystallization structure of polymer melts under a complex flow field. This complex flow field is characteristic of the consistent coupling of extensional “pulse” and closely followed shear flow in a narrow channel. Utilizing an ingenious combination of an advanced micro-injection device and long chain aliphatic polyamides (LCPA),...
The influence of nanoparticle geometry, such as size and shape, on the phase morphology of partially miscible binary polymer blends under and after shear has been examined by rheological and rheo-optical techniques. The phase morphologies of the solution-polymerized styrene-butadiene rubber and low vinyl content polyisoprene (SSBR/LPI) blend systems were affected by the dispersion status of fillers...
Study of the degradation behavior of implants is of crucial importance in biomedical fields before practical applications. In this study, degradability of poly (DL-lactic-co-glycolic acid) (PDLGA)/poly (DL-lactide)-block-poly (ethylene glycol) (PDLA-b-PEG) scaffolds was evaluated both in vitro and in vivo. In vitro degradation of fibrous scaffolds showed that highly porous structure facilitated the...
Transamidation between PA1012 and PA612 was investigated with combination techniques including differential scanning calorimetry (DSC), rheometry, nuclear magnetic resonance (NMR) and variable-temperature Fourier transform infrared spectroscopy (VT-FTIR). Based on the increase of storage modulus with sweep time, the presence of reactive chain ends were proved, promoting chain growth in either polyamide...
A series of random hyperbranched linear polyethylene (RHBLPE), which represents a completely new type of polyethylene, was synthesized through a single step polymerizing process of ethylene by an α-diiminonickel complex pre-catalyst. The molecular weights, branching architectures, chemical compositional distributions as well as the crystallization behavior of these RHBLPEs were carefully investigated...
The correlation between rheological behavior and time evolution of the phase separation patterns was investigated in the epoxy/thermoplastic blends. Before and during the induction period of phase separation, the storage and loss modulus initially increased with epoxy curing reaction and the concentration fluctuation. At the late stage of phase separation, the modulus values also increased and showed...
Crystallization behaviors and kinetics of iPP in an in-situ prepared isotactic polypropylene/graphene (iPP/G) composites were studied in this paper. In samples used in this study, the graphene fillers were well dispersed, and the interfacial adhesion exhibited enhanced features between graphene and iPP components. The thermal stability of the composites was improved by about 100 °C compared to the...
Although recent experiments concerning shear effects on crystallization in polymer melts are inclined to support the oriented network model, two important questions still remain open: the effect of polydispersity on shish formation and the growth mechanism of shish. In this work, a narrowdisperse poly(ethylene oxide) (PEO) is chosen as a model system to clarify the role of polydispersity for shish...
The rheological properties of polybutadiene (PB)/polyisoprene (PI) in the unstable and metastable regions under oscillatory shear flow has been studied. Based on the shear quench experiment, it showed that the time dependent storage modulus G′ initially increased and then decreased with time in the unstable region. The concentration fluctuation led to the increasing part and the coarsening of the...
The structure, porosity and crystallization behavior of poly (L-lactic acid) and poly (L-lactic acid)/polyurethane porous membranes, prepared from ethanol/dioxane and ethanol/water coagulation baths through immersion precipitation, have been systematically investigated. The diffusion rate between solvent and nonsolvent as well as the equilibrium phase diagram of PLLA/solvent/nonsolvent system were...
The effects of wetting induced surface segregation on the crystal nucleation, growth rate, morphology and crystal orientation of melt-miscible crystalline–crystalline diblock copolymer of poly(l-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) thin films (∼90 nm) were investigated in this work with reflection optical microscopy (ROM), atomic force microscopy (AFM), and two-dimensional grazing incident...
Mesophase separation between the incompatible blocks in multiblock copolymers OBC (Olefin Block Copolymers), coupled with the macrophase separation in its blends with iPP (isotactic polypropylene), makes iPP/OBC a unique blend system to understand the interaction between multiple phase separations and the subsequent or simultaneous crystallization in multi-scales. The role played by OBC content as...
Bisphenol-A polycarbonate (PC) and amorphous polyamide (aPA) were used as reactive system to study the interfacial interchange reaction between condensation polymers. Aminolysis is the main process during thermal annealing at 160–180 °C. The simultaneously scission of PC chains and formation of PC-aPA copolymer chains during the reaction process, can act as interfacial compatibilization agents between...
Morphological structure development of the in-situ polymerized isotactic polypropylene/graphene nanocomposites was investigated during the annealing process. The material was prepared via an in-situ slurry polymerization method with graphene-supported Ziegler–Natta catalyst. An interpenetrating network was observed at a relatively low graphene concentration after the sample was annealed for a long...
The growth of transcrystallites induced by fracture stress was studied in the solution casted polystyrene (PS)/poly(ethylene oxide) (PEO) blends films. Both the structure geometry of the crack edge and the effect of local fracture stress on the crystallization were considered. It was found that the local fracture stress contribution is the most important factor to the formation of transcrystallites...
The crystalline/crystalline polymer blend of poly(butylenes succinate)/poly(ethylene oxide) (PBS/PEO) exhibited lower critical solution temperature (LCST) phase separation behavior at temperatures above the melting point of PBS, which was measured by phase contrast optical microscopy (PCOM) technique. In this work, we determined the LCST phase diagram of PBS/PEO blends, and then investigated the effect...
The morphological and rheological responses to the transient and steady shear flow for a phase-separated polybutadiene (PB)/low vinyl content polyisoprene (LPI) blend have been investigated. Under steady shear flow where the applied shear rate is not too large, the steady sheared structures become increasingly anisotropic and interconnected with an “en route” to the formation of string phases as shear...
Time-resolved synchrotron small angle X-ray scattering (SAXS) was used to investigate the early stages of crystallization in melt crystallized polyethylene. Classic Gibbs nucleation or density fluctuation theory can be used to describe the primary nucleation mechanism. At 110 °C, no signal of crystallization can be detected by SAXS for 30 min. When it is lower than 110 °C, the low q scattering intensity...
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