A novel biological friendly shape memory polymer and self-healing polymer based on poly(propylene carbonate) (PPC)/microfibrillated cellulose (MFC) was prepared. MFC was firstly modified by a one-step mechanic-chemical approach involves ball milling and esterification reaction. In this way MFC could be incorporated into PPC up to 20 wt% with excellent dispersion. The formation of "MFC network" structure in the PPC matrix was verified via scanning electron microscopic and the strong interfacial interaction between PPC and MFC was confirmed by X-ray photoelectron spectroscopy. The incorporation of MFC not only significantly enhanced mechanical strength and thermal stability, but also acted as physical cross-linkers, which could improve the shape memory property of PPC at definite content (5~10 wt%). More importantly, with the assistance of shape memory effect and the reinforcement of MFC fibers, the polymer composites also showed much enhanced scratch resistance and scratch self-healing behavior. Our work provides a composite approach to tune the shape memory behaviors of polymer composites and may contribute to the application of PPC in smart materials field.

In this study, green composite films based on cellulose nanocrystal/chitosan (CNC/CS) were fabricated by solution casting. FTIR, XRD, SEM, and TEM characterizations were conducted to determine the structure and morphology of the prepared films. The addition of only 4 wt.% CNC in the CS film improved the tensile strength and Young’s modulus by up to 39% and 78%, respectively. Depending on CNC content, the moisture absorption decreased by 34.1–24.2% and the water solubility decreased by 35.7–26.5% for the composite films compared with neat CS film. The water vapor permeation decreased from 3.83 × 10−11 to 2.41 × 10−11 gm−1 s−1Pa−1 in the CS-based films loaded with (0–8 wt.%) CNC. The water and UV barrier properties of the composite films showed better performance than those of neat CS film. Results suggested that CNC/CS nanocomposite films can be used as a sustainable packaging material in the food industry.

Eco-friendly cellulose nanocrystal/silver/alginate (CNC/Ag/Alg) bionanocomposite films were successfully prepared by blending of CNC with Ag/Alg solution. The CNC was fabricated from cellulose microcrystal (CMC) by acid hydrolysis method. The Ag nanoparticles (AgNPs) were generated by using Alg as a reducing agent through hydrothermal process. AgNPs-included composite films showed characteristic plasmonic effect of the AgNPs with the maximum absorption at 491 nm and they also showed high ultraviolet (UV) barrier properties. The CNC/Ag/Alg composite films were analyzed by using scanning electron microscopy, transmission electron microscopy, optical microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction technique. Depending on the type of nanofillers, tensile strength of the composite films increased by 39–57% and water vapor permeation decreased by 17–36% compared with those of the neat Alg films. The Ag/Alg and CNC/Ag/Alg films showed brown color as detected from the increase of both ‘b’ and ‘a’ parameters by colorimeter. The UV and water barrier properties of Alg based composite films were found higher than the Alg films. The obtained results suggested that the prepared composite films can be used in food packaging applications.

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We studied the crystallization behavior in a diblock copolymer/homopolymer blend system exhibiting "dry-brush" phase behavior in the melt. A nearly symmetric poly(ethylene oxide)-blockpolybutadiene (PEO-b-PB) was blended with a PB homopolymer (h-PB) having approximately the same molecular weight as that of the PB block, thereby yielding the dry-brush blends wherein h-PB was localized in the PB microdomain, causing expansion of PB domain thickness without introducing transformation in microdomain morphology. Even though the lamellar identity of PEO domain retained throughout the blend composition, the lamellar units became increasingly isolated as characterized by the formations of cylindrical and spherical vesicles at high h-PB compositions. Over the major composition range (w h-PB e 0.7), crystallization of PEO blocks in the vesicle wall was able to take place at the undercooling comparable to that of PEO homopolymer, implying that the crystallization mechanism was analogous to the homopolymer crystallization initiated predominantly through heterogeneous nucleation followed by longrange crystal growth. At the compositions (w h-PB g 0.8) where most PEO lamellae formed shells of spherical vesicles in the melt, the crystallization was effectively confined within the individual vesicle, and it only occurred at very deep undercooling (∆T > 70 K). The corresponding isothermal crystallization followed the first-order kinetics prescribed by a nucleation-controlled crystallization wherein the crystallization started from homogeneous nuclei followed by essentially instantaneous crystal growth to fill the vesicle wall. In general, the confinement effect exerted by dry-brush blending was far less effective than the corresponding wet-brush blending.

Metallocene polyethylene (mPE) fractions are recognized as being more homogeneous with respect to short-chain branch (SCB) distribution as compared with unfractionated mPEs. Differential scanning calorimetry and polarized optical microscopy (POM) were used to study the influences of SCB content on the crystallization kinetics, melting behavior, and crystal morphology of four butyl-branched mPE fractions. The parent mPE of the studied fractions was also investigated for comparative purposes. mPE fractions showed a much simpler crystallization behavior as compared with their parent mPE during the cooling experiments. The Ozawa equation was successfully used to analyze the nonisothermal crystallization kinetics of the fractions. The Ozawa exponent n decreased from about 3.5 to 2 as the temperature declined for each fraction, indicating the crystal-growth geometry changed from three-dimensional to two-dimensional. For isothermal crystallization, the fraction with a lesser SCB content exhibited a higher crystallization temperature (T c ) window. The results from the Avrami equation analysis showed the exponent n values were around 3 (with minor variation), which implied that the crystal-growth geometry is pseudo-three-dimensional. Both of the activation energies for nonisothermal and isothermal crystallization were determined for each fraction with Kissinger and Arrhenius-type equations, respectively. Double melting peaks were observed for both nonisothermally or isothermally crystallized specimens. The high-melting peak was confirmed induced via the annealing effect during heating scans. The Hoffman-Weeks plot was inapplicable in obtaining the equilibrium melting temperature (T m°) for each fraction. The relationship between T c and T m for the fractions is approximately T m ϭ T c (°C) ϩ 8.3. The POM results indicated that the crystals of parent or fractions formed under cooling conditions did not exhibit the typical spherulitic morphology as a result of the high SCB content.

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