Mo Song

Recent advance in functionalized graphene/polymer nanocomposites

Functionalized graphene (FG) has been considered as one of the next-generation nanofillers for polymer nanocomposites (PNCs) due to its parallel physical properties and cheaper fabricating cost in comparison with carbon nanotubes (CNTs). The development of FG/polymer nanocomposites (FPNs) has been growing very fast in the last five years. It seems to be a suitable time to highlight the recent advances in this field and understand the developing direction of this new member of PNCs. To our best knowledge, this review covers most of the important publications relating to the fabrication, properties and application of FPNs to date.

Polymer/layered clay nanocomposites: 2 polyurethane nanocomposites

A kind of novel polyurethane/Na+-montmorillonite nanocomposites has been synthesised using modified 4,4′-di-phenymethylate diisocyanate (M-MDI), modified polyether polyol (MPP) and Na+-montmorillonite (layered clay). Here, MPP was used as a swelling agent to treat the layered clay. Experimental results indicated that with increasing the amount of layered clay, the strength and strain-at-break increased. The storage modulus below the glass transition temperature of the soft segments in the polyurethane was increased by more than 350%. With increased loading of layered clay, the thermal conductivity decreased slightly rather than increased. This finding will provide valuable information for polyurethane industry.

Preparation of fully exfoliated graphite oxide nanoplatelets in organic solvents

For the first time, fully exfoliated graphite oxide nanoplatelets have been fabricated successfully in a polar organic solvent N,N-dimethylformamide from graphite oxide without any assistance of chemical treatment. The graphite oxide was prepared from expandable graphite by using Hummer’s method.

Preparation and characterisation of covalent polymer functionalized graphene oxide

A covalently bonded polyethylene grafted graphene oxide hybrid material was fabricated successfully. Gamma-aminopropyltriethoxysilane (APTES) was firstly coated onto the graphene oxide sheets, and then maleic anhydride grafted polyethylene (MA-g-PE) was grafted onto the APTES coated graphene oxide sheets, which were confirmed by means of Fourier transform infrared, X-ray photoelectron and differential scanning calorimetry techniques. Functionalization resulted in 96 wt% polymer grafting efficiency, and a 10 °C increase in the crystallisation temperature, compared with that of the pure MA-g-PE. An encapsulating structure of the functionalised graphene oxide sheets was observed by means of TEM. For the potential application of the functionalised graphene oxide, PE/functionalised graphene oxide nanocomposites as an example was assessed in this paper. Initial results showed that Youngs modulus, yielding strength and tensile strength of PE can be improved by incorporation of the PE-graft-graphene oxide at very low loadings. This protocol could broad the potential application of graphene in the development of non-polar polymer/graphene nanocomposites.

The mechanical properties and morphology of a graphite oxide nanoplatelet/polyurethane composite

Significant reinforcement of polyurethane (PU) using graphite oxide nanoplatelets (GONPs) is reported. Morphologic study shows that, due to the formation of chemical bonding, there is a strong interaction between the GONPs and the hard segment of the PU, which allows effective load transfer. The GONPs can prevent the formation of crystalline hard segments due to their two-dimensional structure. With the incorporation of 4.4 wt% of GONPs, the Youngs modulus and hardness of the PU are significantly increased by approximately 900% and approximately 327%, respectively. The resultant high resistance to scratching indicates promise for application of these composite materials in surface coating.

Localized thermal analysis using a miniaturized resistive probe

We describe a novel thermal characterization technique based on a differential arrangement, which achieves spatially localized calorimetric analysis. It involves the use of an active probe which acts both as a highly localized heat source and a thermometer. This ability opens the way for the implementation of scanning calorimetric microscopy where image contrast will be created from thermal analysis data. For a number of polymers we have recorded events such as glass transitions, meltings, recrystallizations and thermal decomposition within volumes of material estimated at a few μm3. The data obtained are compared with those obtained from conventional calorimetry and the events registered in both cases are found to match. For a full quantitative analysis of the results obtained, mathematical modelling of the operation of the technique, taking account of physical and other changes in materials, is required.

Self-assembly of the symmetric diblock copolymer in a confined state: Monte Carlo simulation

Self-assembly of symmetric diblock copolymers in confined state has been investigated by means of Monte Carlo simulation method. The symmetric diblock copolymers were confined in two- (parallel walls or circle) or in three-dimensional (spherical or cylindrical) space. There are interactions between these boundaries and the symmetric diblock polymers. These interactions and boundary shape resulted in the formation of novel self-assemble structures, e.g., strip, circle, core-multishell, and multibarrel-layer structures. Simulation results predicated that it is possible to design different phase structures for block copolymers by adjusting boundary shape and boundary-block copolymer interactions.

Preparation and characterisation of polyurethane grafted single-walled carbon nanotubes and derived polyurethane nanocomposites

Polycaprolactone (PCL) polyurethane (PU) grafted single-walled carbon nanotubes (SWNT-g-PU) were synthesized from hydroxyl functionalized single-walled carbon nanotubes (SWNT-OH) through a two-step reaction. Based on SWNT-g-PU, PCL polyurethane (PU)/SWNT nanocomposites were prepared by further in-situ polymerization. The results suggested that SWNT-g-PU improved the dispersion of SWNT in the PU matrix and strengthened the interfacial interaction between the PU and SWNT. The incorporation of SWNT-g-PU in the PU matrix improved the phase separation and the degree of crystallization of PCL soft segments, improved the thermal stability and depressed the increment of heat capacity, while pristine SWNT has some slight or inverse effects on these aspects. SWNT-g-PU has a more remarkable effect on Young’s modulus compared with pristine SWNT. At 0.7 wt% SWNT-g-PU concentration, the Young’s modulus was improved by ∼278% compared to the blank PU, and by ∼188% compared to 0.7 wt% ungrafted pristine SWNT/PU. The remarkable reinforcing effects of SWNT-g-PU may be related to better dispersion of SWNT-g-PU and stronger interfacial interactions between the PU and SWNT. This study could open up a new route for the preparation of high performance polyurethane/SWNT composites.

Scanning thermal microscopy: Subsurface imaging, thermal mapping of polymer blends, and localized calorimetry

We have used a platinum/10% rhodium resistance thermal probe to image variations in thermal conductivity or diffusivity at micron resolution and to perform localized calorimetry. The probe is used as an active device that acts both as a highly localized heat source and detector; by generating and detecting evanescent temperature waves, we may control the maximum depth of sample that is imaged. Earlier work has shown that subsurface images of metal particles buried in a polymer matrix are consistent with computer simulations of heat flows and temperature profiles, predicting that a 1 μm radius probe in air will give a lateral resolution of ∼200 nm near the surface, with a depth detection of a few μm. We have a special interest in polymer blends, and we present zero‐frequency mode and temperature‐modulation mode thermal images of some immiscible blends in which the image contrast arises from differences in thermal conductivity/diffusivity between single polymer domains. The behavior of domains is observed i...

Modulated differential scanning calorimetry: 6. Thermal characterization of multicomponent polymers and interfaces

A quantitative thermal method of determining the weight fraction of interface and the extent of phase separation in polymer materials is described. It is based on the differential of heat capacity signal from modulated-temperature differential scanning calorimetry. By measurement of the increment of heat capacity at the glass transition temperature, the total interface content can be determined. The method assumes that the interface and the rest of the system can be modelled as a series of discrete fractions each with its own glass transition temperature. Several examples, including block copolymers, block copolymers blended with homopolymer, and two-phase and four-phase systems are given to illustrate the range of the method. The calculated results were close to the experimental data for two-phase and four-phase systems.