editorial stimuli-responsive polymers: design, synthesis...

EditorialStimuli-Responsive Polymers: Design, Synthesis,Characterization, and Applications

Dong Wang,1 Matthew D. Green,2 Kai Chen,3

Chalongrat Daengngam,4 and Yohei Kotsuchibashi5

1Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA 24061, USA2Department of Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University,Tempe, AZ 85287-6106, USA3International Center for Material Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 3050044, Japan4Department of Physics, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand5Department of Materials and Life Science, Shizuoka Institute of Science and Technology, Fukuroi, Shizuoka 4378555, Japan

Correspondence should be addressed to Dong Wang; [email protected]

Received 4 July 2016; Accepted 5 July 2016

Copyright © 2016 Dong Wang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Stimuli-responsive polymers or so-called “smart polymers”are macromolecules that are sensitive to certain triggers fromthe external environment, including temperature, light, elec-trical or magnetic fields, and chemicals. The activated poly-mers produce observable or detectable micro- or nanoscalechanges, such as morphology, molecular bond rearrange-ment/cleavage, and molecular motion, which can inducechanges in their macroscopic properties such as color, shape,and functionality. Due to the versatile selection of backboneand functional groups, stimuli-responsive polymers can betailored to have a variety of specific mechanical, chemical,electrical, optical, biological, or other properties and can beengineered into different forms, including bulk, thin film,micro/nanoparticles, and composites. Over the years, manymultidisciplinary efforts have been conducted and reportedoptimizing the functionality of stimuli-responsive polymersand exploring new and innovative applications. However,as shown below, original and exciting research in emergingsectors continues to drive the evolution of and interest in thisclass of polymer.

After a rigorous peer review process, eight articles werecompiled into this special issue as an effort to representthe most recent developments in this field. A variety oftopics are included in this special issue such as experimentaland theoretical modeling efforts with a range of applica-tions, including sensing, biomedical devices, polymer layers,

hydrogels, nanocomposites, shape-memory polymers, andpolymer gels for agriculture.

Tuning the adhesion properties of polymers, surfaces, andhydrogels plays a very important role in fields such as mem-brane technology, biomanufacturing, and tissue engineering.In the paper titled “Combinational Effect of Cell AdhesionBiomolecules and Their Immobilized Polymer Property toEnhance Cell-Selective Adhesion” polymeric substrates withpreselected hydrophobicity are modified with biomoleculesto promote cell-selective adhesion.Thesematerials offer greatpotential for tissue engineering and cell sorting technologies.Similarly, the adsorption characteristics of a polymer gel arestudied in the paper titled “Protein Adsorption onHybrids ofThermoresponsive Polymers and Single-Walled CarbonNan-otubes.” The authors investigate the random adsorption ofRecA proteins onto hybrids containing PNIPAm and single-walled carbon nanotubes (SWNTs) while in the presence orabsence of DNA molecules. The thermoresponsive characterof PNIPAm is used to regulate protein adsorption. Thesefindings open the door to the nanobiodevices usingPNIPAm-SWNT hybrids.

Developments in the field of hydrogels for wound heal-ing and drug delivery have revolutionized approaches totreating chronic skin wounds, cancer therapies, and manyother diseases. The paper titled “Fabrication of Hyaluronan-Poly(vinylphosphonic acid)-Chitosan Hydrogel for Wound

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2016, Article ID 6480259, 2 pageshttp://dx.doi.org/10.1155/2016/6480259

2 International Journal of Polymer Science

Healing Application” reports the fabrication and character-ization of a new hydrogel with a three-dimensional highlyporous structure, short gelation time, high degradation rate,and the ability to prevent E. coli infections. Such a hydrogelhas great potential to be used as bioadhesive for skin woundhealing applications. Also, the paper titled “Incorporationof Amphipathic Diblock Copolymer in Lipid Bilayer forImproving pH Responsiveness” studies how changes in envi-ronmental pH cause a change in the bilayer fluidity, whichregulates the release rate of doxorubicin. Such improvedpH-controllability over the drug release from hybrid lipo-somes offers new insights into the design of drug deliverysystems. Another drug delivery approach utilizing stimuli-responsive polymers is reported in “Magnetically TriggeredMonodispersed Nanocomposite Fabricated by MicrofluidicApproach for Drug Delivery.” In this paper, a nanocompositegel consisting of PNIPAm, which is a gel that can swell orshrink in response to temperature or pH, and magnetic ironoxide nanobeads is developed for controlled release of liquiddrugs upon exposure to an alternating magnetic field. Drugrelease from such nanocomposites can be remotely triggeredby a magnetic field and heated through magnetic losses,which presents an innovative strategy for targeted and user-controlled drug delivery.

The properties of stimuli-responsive polymers can also beharnessed for sensing applications. For example, the papertitled “Electrospun PEDOT:PSS/PVP Nanofibers for COGas Sensing with Quartz Crystal Microbalance Technique”reports on the effects of the surface area of PEDOT:PSS/PVPnanofiber membranes on the adsorption of CO. The adsorp-tion process triggers a change in the oscillation frequency,which enables sensitivity to low concentration (5–50 ppm) ofCO with a linear relation to the resonant frequency.

Modeling and simulating polymeric systems providecritical information about the molecular processes that gov-ern polymer properties and phenomena. These powerfultools can be used to study a great variety of polymerproperties, systems, and behaviors. In the paper “ModelingBased Characterization of Thermorheological Properties ofPolyurethane ESTANE�” the commercially available shape-memory polymer, ESTANE, is investigated using DynamicMechanical Thermal Analysis (DMTA). The coefficient ofthermal expansion above and below the glass transitiontemperature is estimated and a finite viscoelastic and incom-pressible material model is used to predict the viscoelasticproperties observed in the uniaxial stress relaxation experi-ments. This work may provide the necessary knowledge basefor further progress in the development of shape-memorypolymers. Also, modeling stimuli-responsive polymers canshed light on agricultural and biological research.An exampleis demonstrated in the paper titled “Phase Characterizationof Cucumber Growth: A Chemical Gel Model.” The effectof hydrogel swelling in both pre- and postharvest stageson cucumber growth is studied. In fruit development, thehormones stimulate the expansion of cells, which is similarto the swelling mechanism of the hydrogel. The model offerssolutions to regulate fruit development and can be extendedto other plant candidates for potential biological and foodengineering.

We believe the research reported in this issue can enrichthe basic understandings and stimulate further developmentof these advanced smart materials.

Acknowledgments

We appreciate the great efforts and contributions from theauthors and reviewers to the special issue.

Dong WangMatthew D. Green

Kai ChenChalongrat Daengngam

Yohei Kotsuchibashi

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