IRBM

Minko S.

Urban M.W.

While the design of responsive and/or proactive polymeric chains mimicking biological systems are essential building blocks for future developments of smart coatings, the physico‐chemical aspects of processes associated with the film formation are equally important. Chemistries that are key enablers to many next‐generation materials that will become capable of mimicking biological systems involve amino acids, hydroxyls, phosphate esters, acetyls, thiols, acryloamides, and carboxyl‐terminated species. Equally important is how these species may generate various forms of responsiveness in synthetic polymers, either by chemical reactions with other groups, or hydrophilic and/or hydrophobic interactions where the placement of oligosacchrides, peptides, or nucleaic acid groups in a specific position will generate intra and intermolecular interactions leading to supramolecular assemblies. Regardless of internal or external stimuli, typical responses lead to shape, size, and orientation changes, which is why the ...

Matheson R.R.

McCormick C.L., Kirkland S.E., York A.W.

Urban M.W., Lestage D.

Colloidal dispersions stabilized by biologically active dispersing agents such as phospholipids have become of significant interest due to the ability of manipulating polymer morphologies through tailoring synthetic and surface properties. As a result, unique particle morphologies ranging from hollow, cocklebur, and tubular shapes can be obtained. This review outlines recent advances in this field and discusses the role of bioactive phospholipids on generation these morphologies as well as film formation processes. Various possibilities and opportunities resulting from stimuli-responsive film formation and stratification processes stimulated by solution ionic strength, pH, enzyme concentration, and temperature are discussed. The control stratification and mobility during and after coalescence are the key factors in developing lipid rafts. Stimuli-responsive behaviors of colloidal films, if accurately controlled, offer a number of opportunities in their utilization for medical, sensing, and other devices.

Yoshida M., Langer R., Lendlein A., Lahann J.

Kharlampieva E., Sukhishvili S.A.

New developments in the area of hydrogen‐bonded layer‐by‐layer assembly composed of weak polyelectrolytes are reviewed, with emphasis on self‐assembly in an aqueous environment. Advances in fundamental understanding of polymer layering at surfaces are addressed. The effects of molecular weight of polymers, ionic strength, pH, and temperature on growth and post‐self‐assembly response of hydrogen‐bonded films are summarized and contrasted with trends known for electrostatically assembled films. Deposition of hydrogen‐bonded films onto particulate substrates and properties of produced capsules are discussed. Strategies to stabilize hydrogen‐bonded multilayers at neutral and basic pH through crosslinking and response properties of produced ultrathin hydrogel films deposited onto flat substrates or comprising the wall of capsules are also described. The potential of hydrogen‐bonding self‐assembly in surface modification and functionalization, in construction of responsive functional containers and membranes, o...

Herring A.M.

Composite membranes consisting primarily of a polymer and an inorganic proton conducting particle or a proton conducting polymer containing inorganic particles for use as proton exchange membranes in low and intermediate temperature fuel cells are reviewed. The chemistry of major inorganic additives that have been used is described in terms of their structure and intrinsic ability to conduct protons. Composites are classified in terms of four main classes: inorganic proton conductors suspended in inert polymers; inorganic particles added to extend polymeric ionomers; inorganic proton conductors blended with polymeric ionomers; and polymer acid complexes between basic polymers and acidic inorganic particles.

Zawodzinski T.A., Schiraldi D.

Nandan B., Hsu J., Chen H.

Block copolymers show interesting phase behavior if at least one of the constituting blocks is crystallizable. The morphology development becomes highly complex when such a block copolymer is crystallized above the glass transition temperature of the amorphous block due to competition between microphase separation and crystallization during the structure evolution process. In this review, we focus on the morphology development in such crystalline‐amorphous (C‐A) diblock copolymers where the amorphous block remains rubbery during the crystallization process. Crystallization behavior in bulk as well as in thin films is considered. The issue of crystal orientation and chain folding upon crystallization in these diblock copolymers has been discussed. Moreover, the nucleation mechanism in these C‐A diblock copolymers and its effect on their crystallization kinetics is also described. Some of the emerging areas of research such as crystallization behavior in blend of C‐A diblock copolymers has been briefly disc...

Perpall M.W., Smith D.W., DesMarteau D.D., Creager S.E.

An alternative fluoropolymer and carbon composite materials approach for proton exchange membrane (PEM) applications is reviewed based on non‐PFSA polymers derived from unique trifluorovinyl ether (TVE) compounds. Radical polymerization and copolymerization of perfluoroalkyl TVE monomers give perfluoroalkylsulfonyl imide ionomers which behave similarly to Nafion™ membranes, yet demonstrate higher acidity and greater stability. Aromatic TVE monomers incorporating the perfluoroalkylsulfonimide functionality undergo thermal step‐growth polymerization to perfluorocyclobutyl (PFCB) polymers and unique ionomers. PFCB containing sulfonated polyarylene ether sulfone ionomers, as well as directly sulfonated PFCB polymers have been synthesized in a prefunctionalization method. Designed carbon/fluoropolymer composite electrodes with porous architectures and covalently attached fluoropolymers are also reviewed.

Halperin A.

The distinctive features of polymeric surfactants as compared to monomeric, low molecular amphiphiles are reviewed from a theoretical point of view. The relative importance of the configurational entropy is discussed and illustrated for polymeric micelles formed from three different types of diblock copolymers. When the number of amphiphilic motifs within the polymer increases, distinctively polymeric features appear. Bridging and exchange interactions play an important role when the number of blocks is three and above. This gives rise to the formation of physical gels. Intrachain self‐assembly occurs in multiblock copolymers and polysoaps and affects the configurations, dimensions and elasticity of the single chain.

Schiraldi D.A.

Durability is a critical issue in all fuel cell systems, certainly so for PEM membrane polymers. Perfluorinated ionomers are generally favored in PEM systems at the present time; the useful lifetimes of such systems can be limited by damage including membrane thinning, weight loss, and redistribution of catalyst materials during fuel cell operation. Hydrogen peroxide remains the most likely culprit for membrane degradation, being readily produced as a by‐product under fuel cell catalysis conditions. Once generated, hydrogen peroxide can be readily homolysed into peroxide radicals capable of breaking of polymer constituent bonds. The leading mechanism for degradation of commercially‐available PEM membranes is initiated by abstraction of a hydrogen atom from residual carboxylic acid ends on PTFE backbones. Such atom abstraction initiates a systematic chain oxidation to carbon dioxide and hydrogen fluoride, which is detected in the effluent water. Reduction of the carboxylic acid ends by fluorination substan...

Hamrock S.J., Yandrasits M.A.

Douglas E.P.