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In 1968, Heskins and Guillet published the first systematic study of the phase diagram of poly(N-isopropylacrylamide) (PNIPAM), at the time a "young polymer" first synthesized in 1956. Since then, PNIPAM became the leading member of the growing families of thermoresponsive polymers and of stimuli-responsive, "smart" polymers in general. Its thermal response is unanimously attributed to its phase behavior. Yet, in spite of 50 years of research, a coherent quantitative picture remains elusive. In this Review we survey the reported phase diagrams, discuss the differences and comment on theoretical ideas regarding their possible origins. We aim to alert the PNIPAM community to open questions in this reputably mature domain.

The adsorption of model proteins onto brush-coated surfaces can occur via two modes. Primary adsorption at the surface, where short range attraction is dominant, is important for small proteins and may be repressed by increasing the grafting density. Secondary adsorption, due to van der Waals attraction, occurs at the outer edge of the brush. Large rodlike proteins are likely to adsorb in this fashion. This mode may be repressed by increasing the brush thickness. The thermodynamics and kinetics of adsorption of model proteins are considered within a simple analytical theory distinguishing between the different adsorption mechanisms of small and big proteins.

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A scaling theory is given for the structure of micelles formed by A-B diblock copolymers in a highly selective solvent. We consider micelles consisting of a small insoluble B core and an extended soluble A corona, i.e., the case )VA » NB (NA and NB are the polymerization degrees of the A and B blocks). The analysis is based on the Daoud-Cotton model for star polymers. It is found that the core radius scales as IVb3/5 while the overall micelle radius scales as NB4/15NAS/6.

The identification of design criteria for the prevention of surface fouling by protein adsorption has been an elusive research goal. The current ideas in this domain assume two different directions. One focuses on correlating protein adsorption with macroscopic surface properties such as the water wettability. The second approach involves tailoring the molecular interactions between the adsorbing proteins and the surface. In this paper, we focus on the experimental results and theoretical ideas concerned with tuning the interfacial forces by means of terminally grafted PEO chains.

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A scaling analysis of the deformation behaviour of a collapsed linear coil in a poor solvent is presented. The elastic response of an ideal coil is found for strong deformations. The response to weaker deformations is dominated by the surface free energy: for weak deformations linear response is expected. Intermediate deformations result in nonlinear response. In particular, the restoring force, f, for intermediate stretching scales asf-Lo and as f -L-' for compression, where L is the globule size along the direction of the force. The novel f -L o regime is reminiscent of a fist-order phase transition from a collapsed globule to stretched coil.