AmericanChemicalSociety.com

In the frames of  the 236th ACS National Meeting, August 17-20, 2008, a  3-day PMSE Symposium titled” Responsive and Interactive Polymer Materials and Multicomponent Systems” was organized by Sergiy Minko (Clarkson University) , Igor Luzinov (Clemson Univ), Marcus Mueller  (University of Goettingen), Manfred Stamm (IPF Dresden). The symposium encountered a number of lectures presented by highly recognized scientists in the field. Seven sessions covered all major directions of the field and were well attended (in average 75-100 attendees) and well accepted by the audience. The symposium was very successful in presenting a snapshot of the current state-of-the-art in this rapidly evolving field and summarized recent, exciting developments, new applications and challenging fundamental questions.

The symposium summarized major conclusions in the field of responsive polymer materials which can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species upon external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal, and mechanical signals and vice versa.  These materials have played an increasingly important role in a diverse range of applications, such as drug delivery, diagnostic, tissue engineering, and “smart” optical systems, as well as biosensors, microelectro-mechanical systems (MEMS), coatings, and textiles.  We symposium reviewed recent advances and challenges in the methods of fabrication, design, and properties of stimuli-responsive polymer materials as well as the underlying physical principles and theoretical approaches. The speakers provided a critical overview of the current state, discussed the interplay between different application areas, and outlined prospective developments.

 The presentations discussed common fundamental principles and mechanisms utilized in stimuli-responsive polymer materials and systems, as well as challenges for theory and simulations.  In fact, the design and application of responsive polymer materials require a molecular understanding of the interplay between individual polymer conformations (e.g., in brushes, micelles, networks, and thin films), their ability to collectively respond to changes in their chemical and physical environment (e.g, electrochemical conditions), and the morphology of these multi-component systems on a scale from nanometers to microns. Their functions (e.g., tuning wettability or adhesion, controlling protein adsorption or permeability, motion of nano-objects) rely on distinct but highly correlated structural properties (e.g., average surface composition and charge, length scale of morphology, fluctuation and memory effects, kinetics).

Speakers addressed recent major advantages in stimuli-driven self-assembly and stimuli-responsive colloidal systems.  Self-assembly is the major tool of the bottom-up approach for creation of multifunctional materials as integrated systems constituted of molecules and particulates. The meeting discussed how specially selected functional building blocks (amphiphilic and ampholitic polymer molecules, functional nanoparticles, magnetic particulates) can be coordinated by external stimuli to form self-assembling functional materials and how the external stimuli can be employed to regulate, tune, and switch material properties in these integrated systems. These systems have recently offered remarkable possibilities for the development of “smart” dispersions, foams, emulsions, magnetic liquids, and drug delivery capsules.

The sessions reviewed adjustable interfaces and thin films, which reconstruct under various external stimuli. If multi-component polymer materials are exposed to external stimuli (e.g., solvents or mechanical stress), their surface structures will reversibly respond. This discussion indentified the common features and differences between different structural geometries (brushes, thin films, networks, and capsules), which have been exploited to control and switch a variety of properties including wettability, adhesion, permeability, optical appearance, and compliance. These effects are the basis for applications like, for instance, sensors or drug delivery systems.