Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

Emerging applications of stimuli-responsive polymer materials

Future perspectives and recent advances in stimuli-responsive materials

Oral drug delivery with polymeric nanoparticles: the gastrointestinal mucus barriers.

Responsive polymers in controlled drug delivery

Liposomes and nanoparticles: nanosized vehicles for drug delivery in cancer.

A semi-interpenetrating polymer network (IPN) of polyvinyl alcohol (PVA) and poly(acrylamide-co-styrene) (PAMS) was prepared and its potential for controlled release of tetracycline was assessed. The IPN was characterized by IR spectral analysis and network parameters such as the average molecular weight between crosslinks (M_c), crosslink density (q) and number of elastically effective chains (V_e) were evaluated. The influence of various experimental conditions such as different percent loadings, composition of the IPNs, thickness of the loaded device, pH and nature of the release medium were investigated on the release profiles of the drug. Various kinetic constants such as the diffusional exponent (n), diffusion constant (D) and penetration velocity (v) were evaluated for different release processes and based on the dynamic release data, an analysis of transport mechanisms of tetracycline was made using Fick's equations.

Release dynamics of tetracycline from a loaded semi-interpenetrating polymeric material of polyvinyl alcohol and poly(acrylamide-co-styrene)

A hydrophilic macromolecular network containing hydrophobic moieties has been prepared by free radical copolymerization of acrylamide and styrene in the presence of poly(vinyl alcohol) (PVA) and its potential as controlled drug delivery carrier was evaluated with tetracycline as a model antibiotic drug. The amount of drug was assayed spectrophotometrically. The network was characterized by optical microscopy, infra-red spectroscopy and structural parameters such as average molecular weight between crosslinks (M
 c
 ), crosslink density (q) and number of elastically effective chains (V
 e
 ) were evaluated. It was found that with increasing concentration of PVA, ST and MBA in the hydrogel, the release rate initially increases but after definite concentrations of the above components the release rate falls. In the case of AM, release rate constantly decreases with increasing AM concentration in the hydrogel.

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Swelling controlled delivery of antibiotic from a hydrophilic macromolecular matrix with hydrophobic moieties

The water sorption dynamics of a binary interpenetrating polymer network (IPN) composed of polyvinyl alcohol (PVA) and poly(acrylamide‐co‐acrylic acid) was studied gravimetrically. The IPN was characterized by IR spectral analysis and various network parameters such as molecular weight between crosslinks (M c), crosslink density (q) and number of elastically effective chains (V e) were also evaluated. The effects of various parameters such as composition of the IPN, pH, and temperature of the swelling medium and addition of inorganic salts were investigated on the kinetics of the swelling process. The dynamic swelling parameters such as the swelling exponent, diffusion constants and penetration velocity were evaluated and the possible mechanisms of water sorption were evolved on the basis of the swelling exponent (n), diffusion constant (D), and penetration velocity (v). The enthalpy of mixing of the IPN and the solvent (water) was also calculated using the Gibbs–Helmholtz equation.

Modulation in Sorption Dynamics of a pH‐Sensitive Interpenetrating Polymer Network (IPN)

A macromolecular vehicle entrapping crystal violet (CV) as a model drug was developed by crosslink polymerization of acrylamide and styrene in the presence of a hydrophilic polymer poly(vinyl alcohol). The loaded polymer matrix was monitored for the controlled release of the crystal violet by a spectrophotometric method. The dynamics of the release process was investigated as a function of the composition of the gel and pH of the release medium. The mechanism of the release process was examined kinetically in terms of the quantitative parameters such as the diffusional exponent n and diffusion constant D evaluated using the Ficks equations.

Sandeep Shukla

Papers

Responsive polymers in controlled drug delivery

Release dynamics of tetracycline from a loaded semi-interpenetrating polymeric material of polyvinyl alcohol and poly(acrylamide-co-styrene)

Swelling controlled delivery of antibiotic from a hydrophilic macromolecular matrix with hydrophobic moieties

Modulation in Sorption Dynamics of a pH‐Sensitive Interpenetrating Polymer Network (IPN)

Modulation of in vitro release of crystal violet from a binary polymer hydrogel system