The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO2 in the atmosphere. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO2 buildup. This review covers six important CO2 transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO2, its synthetic reactions and their possible role in future CO2 mitigation schemes that has to match the scale of man-made CO2 in the atmosphere, which rapidly approaches 1 teraton.

The teraton challenge. A review of fixation and transformation of carbon dioxide

Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions

Polypropylene (PP)−clay hybrids (PPCH) have been prepared by simple melt-mixing of three components, i.e., PP, maleic anhydride modified polypropylene oligomers (PP-MA), and clays intercalated with stearylammonium. The dispersibility of 10-A-thick silicate layers of the clays in the hybrids was investigated by using a transmission electron microscope and X-ray diffractometer. It is found that there are two important factors to achieve the exfoliated and homogeneous dispersion of the layers in the hybrids:  (1) the intercalation capability of the oligomers in the layers and (2) the miscibility of the oligomers with PP. Almost complete hybrids were obtained in the case where the PP-MA has both intercalation capability and miscibility. The hybrids exhibit higher storage moduli compared to those of PP especially in the temperature range from Tg to 90 °C. The highest relative storage modulus at 80 °C of the hybrid based on a mica and the miscible PP-MA is as high as 2.0 to that of PP and is 2.4 to that of the ...

Preparation and Mechanical Properties of Polypropylene−Clay Hybrids

Interest in thermoresponsive polymers has steadily grown over many decades, and a great deal of work has been dedicated to developing temperature sensitive macromolecules that can be crafted into new smart materials. However, the overwhelming majority of previously reported temperature-responsive polymers are based on poly(N-isopropylacrylamide) (PNIPAM), despite the fact that a wide range of other thermoresponsive polymers have demonstrated similar promise for the preparation of adaptive materials. Herein, we aim to highlight recent results that involve thermoresponsive systems that have not yet been as fully considered. Many of these (co)polymers represent clear opportunities for advancements in emerging biomedical and materials fields due to their increased biocompatibility and tuneable response. By highlighting recent examples of newly developed thermoresponsive polymer systems, we hope to promote the development of new generations of smart materials.

New directions in thermoresponsive polymers.

Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer’s physical properties, including absorption, emission, energy level, molecular packing, and charge transport. To date, numerous flexible substituents suitable for constructing side chains have been reported. In this Perspective article, we advocate that the side chain engineering approach can advance better designs for next-generation conjugated polymers.

Side Chain Engineering in Solution-Processable Conjugated Polymers

The solubility of poly(ethyl oxazoline) in aqueous solutions was studied. The cloud point temperatures decreased in the presence of sodium chloride but increased by the addition of tetrabutylammonium bromide or dioxane. Solution-cast films of blends of the polymer and poly(acrylic acid) were miscible, but mutual precipitation occurred in water, methanol, and dioxane. The compositions of the complexes correspond in most cases to simple molar ratios of the interacting groups. The glass transition temperatures of the complexes are higher than the values for blends of the same compositions, and the high values are attributed to hydrogen bonds acting as physical crosslinks. Complex formation also occurs when the polymer is mixed with a styrene-acrylic acid copolymer and with low weight polymers containing phenol groups.

Solubility and miscibility of poly(ethyl oxazoline)

Correlation between the glass transition temperatures of polymer mixtures and intermolecular force parameters

Mutual precipitates of poly (N, N-dimethyl acrylamide) and poly (4-hydroxystyrene) were collected from dioxane, methanol, or acetone. The glass transition (Tg) temperatures of the precipitates are higher than the weight-average values. Clear films cast from dimethylformamide solutions have lower Tg values. Complexation also occurred between poly (ethyl oxazoline) and poly (4-hydroxystyrene) in dioxane and between poly (vinyl pyrrolidone) and poly (4-hydroxystyrene) in methanol. Again, the glass transition temperatures of the precipitates are higher than the values for the blend films. The ΔCp values associated with the glass transitions of the complexes are smaller than those of the blends having the same compositions. Negative excess heat capacities of mixing have been observed for several precipitates.

Glass transitions in hydrogen‐bonded polymer complexes

Partially modified polystyrene containing vinyl phenyl hexafluorodimethyl carbinol was mixed with a number of counterpolymers containing poly(vinyl-acetate), poly(methyl methacry1 ate), poly(ethy] methacrylate, poly (n-butyl methacry late), poly(viny] methyl ether), poly(2,6 dimethyl-1,4 phenylene oxide), bisphenol A polycarbonate poly(styrene-co-acryloni-trile), poly (dimethyl siloxane), a crystallizable polyester, an amorphous polyamide and two amorphous polyamides. Hydrogen bonding interactions to effect miscibility were related to the number of proton donating groups in the modified polystyrene, and these were studied in regard to lower critical solution temperatures and the glass transition temperatures of the hydrogen bonded blends.

Polymer Compatibilization Through Hydrogen Bonding

The structures of unoriented films of poly(3-alkylthiophenes) were studied by X-ray diffraction, IR spectroscopy, and organic vapor sorption. Side-chain crystallization takes place in these films when the alkyl groups contain 12 or more carbon atoms. The disordering of the side chain upon melting results in a large increase in the amount of hexane vapor absorbed by poly(3-tetradecylthiophene) (PTDT) when the temperature is raised to above the melting point. The effective distance of side-chain overlap, an measured by hexane as the diffusional probe, is estimated to be 6.7 A along the α-axis

T. K. Kwei

Papers

Solubility and miscibility of poly(ethyl oxazoline)

Correlation between the glass transition temperatures of polymer mixtures and intermolecular force parameters

Glass transitions in hydrogen‐bonded polymer complexes

Polymer Compatibilization Through Hydrogen Bonding

Side-chain order in poly(3-alkylthiophenes)