Special Issue "Stimuli-Responsive Polymers and Colloids"

Guest Editor
Prof. Dr. Michael K.C. Tam
Department of Chemical Engineering, University of Waterloo, Waterloo Institute for Nanotechnology, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
Website: http://chemeng.uwaterloo.ca/faculty/tam.html
E-Mail: mkctam@uwaterloo.ca
Phone: +1 519 888 4567
Fax: +1 519 888 4347
Interests: stimuli-responsive polymers; self assembly; polymer-surfactant interactions; drug delivery; renewable nanomaterials

Dear Colleagues,

Interest in the field of stimuli-responsive systems has intensified over the last ten years due to the considerable potential of such systems in many applications. Many different external stimuli, such as pH, temperature, light, salt, co-solvent, electric fields, etc. have been explored. With the development of many controlled polymerization techniques, it is now possible to prepare a wide range of amphiphilic polymers and colloidal systems that possess many types of stimuli-responsive characteristics. Many of these systems possess interesting self-assembling and swelling characteristics when subjected to external stimuli.

This special issue of Polymers entitled “Stimuli-Responsive Polymers and Colloids” will cover a range of recent research activities such as synthesis, physical properties, and applications. It will bring together an interesting collection of recent findings from experts, and will be a useful source of information for researchers working in this field. Your contribution to the special issue will be greatly appreciated.

Prof. Dr. Michael K.C. Tam
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 500 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Type of Paper: Review
Title: Temperature-Responsive Polymer Modified Surface for Cell Culture
Authors: Zhonglan Tang, Yoshikatsu Akiyama and Teruo Okano
Affiliation: Institute of Advanced Biomedical Engineering and Science, Tokyo Women’s Medical University; E-Mails: zltang@abmes.twmu.ac.jp; yakiyama@abmes.twmu.ac.jp
Abstract: In the past decades, a novel approach for tissues engineering, cell sheet engineering, have been proposed by our laboratory. Poly(N-isopropylacrylamide) (PIPAAm), which is a well-known temperature-responsive polymer, was introduced on tissue culture polystyrene (TCPS) surfaces by using electron beam irradiated polymerization. At 37 °C, where the PIPAAm modified surface was hydrophobic, cells could adhere and spread on the surface, and grew to confluence. When decreasing the temperature to 20 °C, since the surface turn to hydrophilic, cells detached from the surface spontaneously and formed an intact cell sheet. In order to express the temperature-induced cell attachment and detachment, ultra thin PIPAAm layer is necessary to be immobilized on TCPS surfaces. This review focus on characteristics of the PIAPAm modified surfaces exhibiting such intelligent properties. In addition, the PIPAAm modified surfaces allowing rapid recovery of cell sheet is further developed on the basis of the characteristic of the PIPAAm surface. These designs of temperature-responsive polymer provide enormous potential for fabricating clinically applicable regenerative medicine.

Title: Stimuli-Responsive Intrinsically Conducting Polymers and Colloids
Authors: Jorge Romero-García, et al.
Affiliation: E-Mail: jromero@ciqa.mx
Abstract: Since their discovery the so-called intrinsically conducting polymers (e.g., polyaniline, polypyrrole) have received ever-increasing attention. This class of materials is widely used in several applications in areas of organic electronics, sensors, actuators, separation technology, corrosion prevention, and storage energy among others. One of the main concerns with the application of the intrinsically conducting polymers (ICP) is their poor processability. To overcome this problem, several strategies have been proposed, among others, the use of substituted monomers, different organic acids as doping agents, and the preparation of ICP aqueous colloidal dispersions. The synthesis of ICP colloids has been achieved by using several inorganic, organic compounds, and polymers as steric stabilizers. An interesting aspect of ICP colloid synthesis is the use of the so-called smart polymers as steric stabilizers. Smart polymers have the ability to respond to external stimuli and provide new functionalities to the ICP polymer dispersions. These new structures acquired smart behaviour because the nature of the attached polymer mainly on the surface of the colloids and thereby can respond to changes in parameters such as pH, temperature, and to the presence of certain metallic ions, electrical field, and biomolecules. The primary focus of this review is to highlight the different approaches to prepare stimuli-responsive ICP colloids, and specifically, how the steric stabilizers influence the overall behaviour to the above mentioned stimuli for applications as sensors and biosensors.

Type of Paper: Review
Title: Poly(N-vinylcaprolactam), a Polymer to Become the Temperature Responsive Material of Choice for Biomedical and Environmental Applications
Author: Angel Licea-Claverie
Affiliation: Instituto Tecnologico de Tijuana, Centro de Graduados e Investigacion, A.P. 1166, 22000 Tijuana, B.C., Mexico; E-Mail:aliceac@tectijuana.mx
Abstract: Poly(N-vinylcaprolactam) (PNVCL) is a well studied temperature responsive polymer, only second to poly(N-isopropylacrylamide) (PNIPAAm) the most popular temperature responsive polymer. Both polymers show a similar LCST behaviour in water between 30-32 oC. In both cases the LCST is fully reversible and it has been shown that PNVCL hydrogels show, similar to PNIPAAm hydrogels, a swelling to collapsing transition in water at the same temperature as the LCST. The lack of popularity among researchers for PNVCL compared to PNIPAAm probably has to do with the difficulty of polymerizing NVCL in a controlled fashion. The polymerization kinetics of both monomers is very different and therefore the controlled copolymerization of NVCL with other monomers is more difficult to achieve. Nevertheless there is an important factor that makes PNVCL very attractive for biomedical and environmental applications: it has been reported that PNVCL is biocompatible, a fact that has been not enough demonstrated for PNIPAAm.

Type of Paper: Article
Title: Preperation of Thermo-Responisve Foncitonal Composites by Embedding TiO2/Fe3O4 Nanoparticles
Authors: Junichi Ida, Fumiko Matsushima, Ochi Masanori, Tatsushi Matsuyama, Hideo Yamamoto
Affiliation: Department of Environmental Engineering for Symbiosis, Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachiouji, Tokyo 192-8577, Japan; E-Mail: ida@soka.ac.jp
Abstract: Thermo-responsive functional composites were prepared by embedding two kinds of functional inorganic particles within thermo-responsive microgel. In this study, poly(N-isopropylacrylamide) and calcium alginate were used as thermo-responsive polymer and structure support polymer, respectively. As functional inorganic nanoparticles, TiO2 and Fe3O4 were used. In the experiment, thermo-responsive functional composites were prepared using single tube nozzle by modifying the simple process to prepare thermo-responsive capsule reported in our previous report1).  The experimental results showed that TiO2/Fe3O4 embedded thermo-responsive composites were obtained successfully. The resulting composites exhibited thermo-responsive volume change and photocatalytic activity. Localized heating of thermo-responsive bead containing Fe3O4 was also achieved without raising a bulk solution temperature by focusing laser irradiation on the bead. By using the localized heating property, repeated shrinking-swelling movement (i.e. pumping movement) of the composite was achieved by applying laser irradiation intermittently. Finally, based on the experimental results, the effect of promoted diffusion of substrate and product due to thermo-responsive pumping on the enhancement of phtocatalytic activity was simulated for the composite. The result showed the effectiveness of thermo-responsive pumping to improve the phtocatalytic activity of TiO2 nano particle embedded composite gel. Furthermore, advantage of the composite compared to the TiO2 nano particle is easy handling due to bigger size and magnetic property.