There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

/pdf/graphene-and-graphene-oxide-synthesis-properties-and-2q80uaujok.pdf

Graphene and Graphene Oxide: Synthesis, Properties, and Applications

Graphene based materials: Past, present and future

Recent advances in graphene based polymer composites

Graphene has emerged as a subject of enormous scientific interest due to its exceptional electron transport, mechanical properties, and high surface area. When incorporated appropriately, these atomically thin carbon sheets can significantly improve physical properties of host polymers at extremely small loading. We first review production routes to exfoliated graphite with an emphasis on top-down strategies starting from graphite oxide, including advantages and disadvantages of each method. Then solvent- and melt-based strategies to disperse chemically or thermally reduced graphene oxide in polymers are discussed. Analytical techniques for characterizing particle dimensions, surface characteristics, and dispersion in matrix polymers are also introduced. We summarize electrical, thermal, mechanical, and gas barrier properties of the graphene/polymer nanocomposites. We conclude this review listing current challenges associated with processing and scalability of graphene composites and future perspectives f...

/pdf/graphene-polymer-nanocomposites-19884oy559.pdf

Graphene/Polymer Nanocomposites

Shape memory polymer compositions, articles of manufacture thereof, and methods of preparation and use thereof are described. The shape memory polymer compositions can hold more than one shape in memory. Suitable compositions include at least one hard segment and at least one soft segment. The Ttrans of the hard segment is preferably between -30 and 270 °C. At least one of the hard or soft segments can contain a cross-linkable group, and the segments can be linked by formation of an interpenetrating network or a semi-interpenetrating network, or by physical interactions of the blocks. Objects can be formed into a given shape at a temperature above the Ttrans of the hard segment, and cooled to a temperature below the Ttrans of the soft segment. If the object is subsequently formed into a second shape, the object can return to its original shape by heating the object above the Ttrans of the soft segment and below the Ttrans of the hard segment. The compositions can also include two soft segments which are linked via functional groups which are cleaved in response to application of light, electric field, magnetic field or ultrasound. The cleavage of these groups causes the object to return to its original shape.

/pdf/shape-memory-polymers-21sug7mu2l.pdf

Shape memory polymers

Polyurethanes having shape memory effects

Nanocomposites of waterborne polyurethane (WPU) with functionalized graphene sheets (FGS) were prepared by an in situ method. The morphology observed by transmission electron microscopy showed that pristine nanosize FGS can be finely dispersed in a WPU matrix so that it can efficiently improve the conductivity of WPU. The modulus improvement by the reinforcing effect of FGS was more evident than our previous results of nanocomposites prepared by a physical mixing method, showing that the interactions between FGS and WPU were improved when made by the in situ method. In addition, the FGS enhanced the crystallization of the soft segment of WPU evidently; however, it reduced that of the hard segment. The thermal degradation of WPU was accelerated by FGS.

Properties of Waterborne Polyurethane/ Functionalized Graphene Sheet Nanocomposites Prepared by an in situ Method

Nanocomposites of waterborne polyurethane (WPU) reinforced with functionalized graphene sheets (FGSs) were effectively prepared by casting from a colloidal dispersion of FGS and WPU, and the morphology and physical properties were examined. The finer aqueous FGS dispersions or WPU with smaller particles yielded nanocomposites with enhanced electrical conductivity and thermal resistance due to finely dispersed FGS. The FGS nucleated the crystallization of the polycaprolactone (PCL) segments in WPU and improved its modulus. However, FGS inhibited crystal growth and deteriorated the tensile properties at high deformation, i.e., tensile strength and elongation at break, because the interaction between FGS and WPU hindered the chain rearrangement of WPU in the nanocomposite.

Properties of Graphene/Waterborne Polyurethane Nanocomposites Cast from Colloidal Dispersion Mixtures

This review describes basic chemistry, preparation process, and physical properties of aqueous polyurethane disperisons and the derived films, along with the methods of post treatment to modify the properties. Basic way to render a polyurethane water dispersible without external emulsifier has been described. Regarding the methods of preparation, four major processes are described and compared. Methods to improve the relatively poor water and solvent resistance of aqueous polyurethane dispersions which is introduced by the hydrophilicity and linear structure of polyurethane have been discussed with an emphasis on acrylate incorporations.

Byung Kyu Kim

Papers

Polyurethanes having shape memory effects

Properties of Waterborne Polyurethane/ Functionalized Graphene Sheet Nanocomposites Prepared by an in situ Method

Properties of Graphene/Waterborne Polyurethane Nanocomposites Cast from Colloidal Dispersion Mixtures

Aqueous polyurethane dispersions

Morphology and properties of waterborne polyurethane/clay nanocomposites