Institute of Polymers

Conjugated polymers are promising materials for flexible electronics, with poly(3-hexylthiophene) (P3HT) standing out for its ease of solution-based processing. However, the influence of the molecular arrangement on thermal transport remains less understood, particularly with respect to thin-film thickness. Here, we investigate the in-plane thermal conductivity of P3HT thin films with thicknesses ranging from 12 to 136 nm using transient thermal grating (TTG) spectroscopy, a precise noncontact optical technique. A pronounced thickness dependence is observed, with the highest thermal conductivity of 0.88 W/m·K in the thinnest film and the lowest value of 0.25 W/m·K in the thickest film. The enhancement in thermal conductivity in thinner films is attributed to denser lamellar packing in face-on configurations, an increased contribution of face-on domains, and spatial confinement-induced improvements in short-range ordering within the amorphous regions of thinner films. These findings demonstrate that the film thickness is an effective parameter for tuning in-plane thermal conductivity in P3HT thin films.

Natural polyphenols, particularly quercetin (QUE) and rosmarinic Acid (RA), possess significant synergistic therapeutic potential as potent antioxidants and anti-inflammatories. However, their poor stability, low water solubility, and resulting limited bioavailability severely hinder their effective clinical translation. This study addresses these fundamental limitations by designing a novel advanced drug delivery platform utilizing electrospinning. We have fabricated composite high-molecular-weight poly(L-Lactic Acid) (PLA)/polyethylene glycol (PEG) nanofibers for the simultaneous co-delivery of both QUE and RA, optimizing compound stability and release kinetics. PLA provided mechanical integrity and sustained release properties, while the incorporation of PEG strategically enhanced the mat's wettability, enabling precise control over initial drug dissolution. Comprehensive characterization confirmed uniform, bead-free morphology and high entrapment efficiency for both polyphenols. Crucially, the PLA/PEG blend successfully achieved a biphasic release profile, featuring an initial burst release mediated by PEG followed by a sustained release phase governed by the PLA matrix. Furthermore, the performed in vitro investigations using SH-4 melanoma cells and HaCaT normal keratinocytes revealed that the prepared novel materials containing the polyphenols possessed high anticancer activity to the used cancer cell line. However, the toxicity to the normal cell line is much lower. Therefore, this novel electrospun composite scaffold offers an effective strategy to enhance the stability, control the delivery, and maximize the synergistic therapeutic benefits of quercetin and rosmarinic Acid for applications in areas such as advanced wound care, tissue regeneration, and antitumor therapies.

As representative mechanically interlocked polymers, polyrotaxanes (PRs) present unique challenges in understanding their viscoelasticity due to the dynamic coupling between rings’ sliding and intrinsic backbone chain relaxation. Although substantial progress has been made in characterizing the static architecture of PRs in solution, their dynamic nature remains poorly explored, and existing research mainly reveals the chain motion on short-time scales. Furthermore, the influence of the noncovalent interaction between threaded rings on the macroscopic mechanical response of PR solution has rarely been evaluated. Herein, linear and nonlinear rheological characterizations were performed on polyethylene glycol/α-cyclodextrin (PEG/α-CD) polyrotaxane solutions across various concentration regimes. Scaling and hydrodynamic analyses of specific viscosity indicated the flexible chain behavior of PRs in dimethyl sulfoxide. In the concentrated regime, nonlinear rheological tests with progressively increasing shear strength were employed to elucidate the complex dynamic processes arising from ring sliding and intermolecular hydrogen-bond dissociation. It elucidates that ring sliding can be triggered under moderate shear prior to extensive hydrogen-bond disruption. The characteristic stresses related to the sliding transition, the onset of association network breakdown, and the high-stress limit are quantitatively estimated. The comprehensive understanding of the nonequilibrium, multiscale dynamics of PR solutions highlights the profound influence of hydrogen-bond association on the macroscopic mechanical response of PEG/α-CD PRs in the solution state.

In recent years, significant effort has been devoted to developing smart materials whose mechanical properties can adapt under physical stimuli. Particulate colloidal gels, which behave as solids but can also flow under stress, have emerged as promising candidates. Resulting from the attractive interaction between their constituents, their network architecture exhibits solidlike properties even at very low volume fractions. This structural flexibility allows them to adopt various configurations and store structural information making them highly susceptible to memory effects. Shear flow, applied through rheometry, offers a simple and effective way to tune their properties and imprint a “rheological memory” of the flow history. However, the precise relationship between flow history and viscoelastic response remains elusive, largely due to the limited structural characterization of these systems during flow and after flow cessation. Here, we use ultrasmall-angle x-ray scattering to reveal a strong structural memory in the solid state, where the microstructure formed under shear is retained after flow cessation. We identify two distinct mechanisms of structural memory, as governed by the ratio of viscous to attractive forces, namely, the Mason number. Using recently developed fractal scaling laws, we show that rheology is fully determined by the gel microstructure. Notably, these gels exhibit a double-fractal architecture, highlighting the remarkably broad range of length scales over which these disordered materials are structured. By clarifying how memory is encoded, our results offer strategies to tune shear sensitivity of colloidal gels and design smart materials.

Amphiphilic polymerconetworks (APCNs) are highly interesting materialfor membranes, drug delivery, or tissue engineering since their heterogeneousstructure and interactions allow for the control of the diffusionof molecules differing by architecture, size, and interactions. Weinvestigate the diffusion of hydrophilic and hydrophobic star polymersin model APCNs formed by heterocomplementary end-linking of tetra-poly­(ethyleneglycol) (t-PEG) and tetra-poly­(ε-caprolactone)(t-PCL). Using Fluorescence Recovery After Photobleaching (FRAP) andForced Rayleigh Scattering (FRS), we gain complementary insights intostar polymer transport across different length and time scales. Wecompare the diffusion of hydrophilic t-PEG and hydrophobic t-PCL ofvarious molecular weights across a wide range of APCN polymer volumefractions, swollen in a cosolvent (toluene) and a selective solvent(water). FRS reveals Fickian diffusion for all tracers in APCNs swollenin toluene. In the unentangled regime, the diffusivity of the tracerfollows approximately the expected Rouse scaling for semidilute solutions.Corrections arise for increasing polymer content due to enforcingcontacts with the other type of polymer in the APCN. At larger concentrations,the PEG tracers develop a diffusion behavior, as expected for entangledstar polymers. Since the transition occurs below the expected entanglementconcentration, an additional impact of the strangulation regime islikely. Partial swelling in a selective solvent leads to an enhanceddiffusion behavior as compared to a homogeneously swollen networkat the same polymer volume fraction; however, the concentration dependenceof diffusion agrees best with the strangulation regime, despite anoverall enhanced diffusion. At swelling equilibrium in the selectivesolvent water, the equilibrium degree of swelling, the network morphology,and the diffusion behavior become independent of the preparation conditions.These findings provide insights into the diffusion mechanism of starpolymers within APCNs and contribute to the development of polymer-baseddrug delivery systems for biomedical applications.