Stimuli-responsive polymers are an important class of advanced materials that have lots of applications in biochemistry, biomedicine, optical memory, and cell labeling. The physical and chemical properties of these materials and also their surrounding media could be varied in response to environmental excitation. Temperature-responsive polymers are a significant category of smart polymers, displaying phase separation and cloud points in response to temperature variations in the solution state. Controlling such responses with light has become an interesting research area, because of the advantages of light-responsive materials for the reversible control of the physical and chemical properties of media in systems with tunable intensities. Photochromic compounds are some of the most important light-responsive materials used for the light-control of temperature-responsivity in light- and temperature-responsive polymers. The incorporation of photochromic compounds, such as spiropyran, azobenzene, diarylethene, and spiroxazine, in temperature-responsive polymers results in reversible light-induced variations of lower critical solution temperatures, upper critical solution temperatures, and phase separation temperatures in such systems. The incorporation of o-nitrobenzyl ester photoactive compounds in temperature-responsive polymers can result in irreversible light-induced variations of these characteristics. These variations originate from light-induced polarity changes in the systems resulting from the responses of the light-responsive compounds. Controlling the thermo-responsivity of dual light- and temperature-responsive polymers using light illumination is the main focus of this study, which is beneficial for the development of new dual- or multi-responsive polymers with potential applications in drug- and gene-delivery systems.

Graphene oxide (GO) nanosheets were simultaneously modified and reduced with ethylenediamine (EDA). Then, EDA-treated GO (RGO-NH₂) was exposed to iterative alkylation and amidation reactions to synthesize poly(amidoamine) (PAMAM)-grafted GO nanosheets. Reactions were continued until 4th generation PAMAM was grafted onto GO layers (RGO-4.0GD). FT-IR results confirmed the synthesis of the different structures, while TGA curves showed that the reactions that occurred were non-ideal and PAMAM was not grafted as expected. Also, XRD patterns showed that there is a resistance against the intercalation of nanolayers named stitching. According to the Raman spectra, the modification progression resulted in a more disordered structure of the graphene layers due to grafting PAMAM generations whereas reduction occurred continuously. Morphological studies were performed by recording SEM and TEM images. The results showed that the treated-GO nanosheets re-stack together, while distinguishable edges of nanolayers were observed.

A multi-step process was used to synthesize fluorescent folic acid (FA)-conjugated stimuli-responsive magnetic nanoparticles as anti-cancer drug nanocarriers. Sol–gel processing of tetraethyl orthosilicate and fluorescein isothiocyanate-conjugated 3-aminopropyltriethoxysilane was used to synthesize Fe₃O₄@SiO₂–FITC followed by the distillation precipitation polymerization of 2-hydroxyethyl methacrylate and N,N′-methylenebis(acrylamide) to obtain Fe₃O₄@SiO₂@P(HEMA) nanoparticles. Conjugating with FA and RAFT agent, Fe₃O₄@SiO₂@P(HEMA)@P(NIPAAM-co-AA) nanoparticles were synthesized via the polymerization of N-isopropylacrylamide and acrylic acid. The core–shell structure of nanoparticles was revealed via TEM. Furthermore, the progression of each step was studied by means of FT-IR and TGA. VSM and XRD were used to show that the synthesized nanoparticles retain their superparamagnetic properties. The synthesized nanoparticles exhibited dual thermo- and pH-sensitive behaviours. These nanoparticles were used as nanocarriers of the anti-cancer drug doxorubicin via controlled release in simulated physiological and acidic conditions. In addition, the synthesized nanoparticles showed a relatively non-toxic nature to HeLa cells, whereas cell viability decreased significantly when cells were incubated with DOX-loaded nanoparticles.