In this article, the effects of size and confinement at the nanometre size scale on both the melting temperature, Tm, and the glass transition temperature, Tg, are reviewed. Although there is an accepted thermodynamic model (the Gibbs–Thomson equation) for explaining the shift in the first-order transition, Tm, for confined materials, the depression of the melting point is still not fully understood and clearly requires further investigation. However, the main thrust of the work is a review of the field of confinement and size effects on the glass transition temperature. We present in detail the dynamic, thermodynamic and pseudo-thermodynamic measurements reported for the glass transition in confined geometries for both small molecules confined in nanopores and for ultrathin polymer films. We survey the observations that show that the glass transition temperature decreases, increases, remains the same or even disappears depending upon details of the experimental (or molecular simulation) conditions. Indeed, different behaviours have been observed for the same material depending on the experimental methods used. It seems that the existing theories of Tg are unable to explain the range of behaviours seen at the nanometre size scale, in part because the glass transition phenomenon itself is not fully understood. Importantly, here we conclude that the vast majority of the experiments have been carried out carefully and the results are reproducible. What is currently lacking appears to be an overall view, which accounts for the range of observations. The field seems to be experimentally and empirically driven rather than responding to major theoretical developments.

https://iopscience.iop.org/article/10.1088/0953-8984/17/15/R01/pdf

Effects of confinement on material behaviour at the nanometre size scale

https://www.umsl.edu/~chickosj/JSCPUBS/dsccal.pdf

Reference materials for calorimetry and differential thermal analysis

The different physical aspects of glass transitions are reviewed and models aiming at their explanation are described. The following three main aspects are distinguished: the degree of stability of supercooled liquids with respect to crystallisation; the variation of physical properties of supercooled liquids in metastable equilibrium above the glass transition; the arrest of structural relaxation at the glass transition. The physical significance of computer simulations of glass transitions in simple liquids and the question of a hidden phase transition underlying an observed glass transition are examined critically. In relation to the stability problem, the geometrical constraints operative in typical disordered structures, such as random sphere packings and random covalent networks, are also discussed. A general survey of glass transition phenomena and concepts is presented in an introductory section.

https://iopscience.iop.org/article/10.1088/0034-4885/49/2/002/pdf

Models of the glass transition

Reversible crystallization and the rigid-amorphous phase in semicrystalline macromolecules

Nanofilled polymeric matrices have demonstrated remarkable mechanical, electrical, and thermal properties. In this article we review the processing of carbon nanotube, graphene, and clay montmorillonite platelet as potential nanofillers to form nanocomposites. The various functionalization techniques of modifying the nanofillers to enable interaction with polymers are summarized. The importance of filler dispersion in the polymeric matrix is highlighted. Finally, the challenges and future outlook for nanofilled polymeric composites are presented.

/pdf/polymer-nanocomposites-a-comparison-between-carbon-nanotubes-4w3eq30vq8.pdf

Polymer nanocomposites-A comparison between carbon nanotubes, graphene, and clay as nanofillers

The heat capacity of polystyrene from 0 K to 600 K is reviewed on the basis of measurements on 29 samples reported in the literature. A set of recommended data for amorphous polystyrene is derived. The effect of tacticity on the heat capacity is also evaluated. Entropy and enthalpy functions are calculated. This paper is the fifth in a series of publications which will ultimately cover all heat capacity measurements on linear macromolecules.

Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules. IV. Polypropylene

The equilibrium melting temperature, volume, and enthalpy and entropy changes on melting of poly(ethylene terephthalate) have been analyzed and heats of fusion have been newly measured with an automated scanning calorimeter to yield the following data: 553°K, 16.9 cm3/mole, 2.69 kJ/mole, and 48.6 J/deg/mole, respectively. A more detailed discussion of annealed samples obtained from etched starting materials shows that the density of the noncrystalline regions may be variable.

Equilibrium melting parameters of poly(ethylene terephthalate)

Study of Microphase Separation in Block Copolymers of Styrene and α-Methylstyrene in the Glass Transition Region Using Quantitative Thermal Analysis

The Glass Transition Temperature of Polyethylene

Heat capacity of poly(methyl methacrylate), polyacrylonitrile, poly(methyl acrylate), poly(ethyl acrylate), poly(n‐butyl acrylate), poly(iso‐butyl acrylate), poly(octadecyl acrylate), poly(methacrylic acid), poly(ethyl methacrylate), poly(n‐butyl methacrylate), poly(iso‐butyl methacrylate), poly(hexyl methacrylate), poly(dodecyl methacrylate), poly(octadecyl methacrylate) and polymethacrylamide is reviewed on the basis of measurements on 35 samples reported in the literature. A set of recommended data are derived for each acrylic polymer in the amorphous state. Enthalpy and entropy functions are calculated for poly(methyl methacrylate) and polyacrylonitrile. This is the sixth paper in a series of publications which will ultimately cover all heat capacity measurements on linear macromolecules.

Umesh Gaur

Papers

Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules. IV. Polypropylene

Equilibrium melting parameters of poly(ethylene terephthalate)

Study of Microphase Separation in Block Copolymers of Styrene and α-Methylstyrene in the Glass Transition Region Using Quantitative Thermal Analysis

The Glass Transition Temperature of Polyethylene

Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules VI. Acrylic Polymers