Surface functionalization of cellulose with poly(3-hexylthiophene) via novel oxidative polymerization

Enhanced luminescence sensing performance and increased intrachain order in blended films of P3HT and cellulose nanocrystals

Blended films comprising poly(butyl acrylate) (PBA)-grafted cellulose nanocrystals (CNCs) and poly(3-hexylthiophene) (P3HT), exhibited more intense photoluminescence (PL) and longer PL emission lifetimes compared to pristine P3HT films. Optical absorption and photoluminescence spectra indicated reduced torsional disorder i.e. enhanced backbone planarity in the P3HT@CNC blended composites compared to the bare P3HT. Such molecule-level geometrical modification resulted in both smaller interchain and higher intrachain exciton bandwidth in the blended composites compared to the bare P3HT, because of reduced interchain interactions and enhanced intrachain order. These results indicate a potential switch of the aggregation behavior from dominant H-aggregates to J-aggregates, supported by Raman spectroscopy. The reorganization of micromolecular structure and concomitant macroscopic aggregation of the conjugated polymer chains resulted in a longer conjugation length for the P3HT@CNC blended composites compared to the bare P3HT. Additionally, this nanoscale morphological change produced a reduction in the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap of the blends, evidenced from optical absorption spectra. Classical molecular dynamics simulation studies predicted the probability of enhanced planarity in the polymer backbone following interactions with CNC surfaces. Theoretical results from density functional theory calculations corroborate the experimentally observed reduction of optical bandgap in the blends compared to bare P3HT. The blended composite outperformed the bare P3HT in nitro-group PL sensing tests with a pronounced difference in the reaction kinetics. While the PL quenching dynamics for bare P3HT followed Stern-Volmer kinetics, the P3HT@CNC blended composite exhibited a drastic deviation from the same. This work shows the potential of a functionalized rod-like biopolymer in tuning the optoelectronic properties of a technologically important polymeric organic semiconductor through control of the nanoscale morphology.

Synthesis of Highly Conductive Poly(3-hexylthiophene) by Chemical Oxidative Polymerization Using Surfactant Templates

Poly(3-hexylthiophene) (P3HT) was systematically synthesized by chemical oxidative polymerization in chloroform with ferric chloride (FeCl₃) as the oxidizing agent and various surfactants of the shape templates. The effects of 3HT: FeCl₃ mole ratios, polymerization times, and surfactant types and concentrations on the electrical conductivity, particle shape and size were systematically investigated. Furthermore, dodecylbenzenesulfonic acid (DBSA), p-toluenesulfonic acid (PTSA), sodium dodecyl sulfate (SDS), and sodium dioctyl sulfosuccinate (AOT) were utilized as the surfactant templates. The P3HT synthesized with DBSA at 6 CMC, where CMC stands for the Critical Micelle Concentration of surfactant, provided a higher electrical conductivity than those with PTSA, SDS and AOT. The highest electrical conductivity of P3HT using DBSA was 16.21 ± 1.55 S cm⁻¹ in which the P3HT particle shape was spherical with an average size of 1530 ± 227 nm. The thermal analysis indicated that the P3HT synthesized with the surfactants yielded higher stability and char yields than that of P3HT without. The P3HT_DBSA electrical conductivity was further enhanced by de-doping and doping with HClO₄. At the 10:1 doping mole ratio, the electrical conductivity of dP3HT_DBSA increased by one order of magnitude relative to P3HT_DBSA prior to the de-doping. The highest electrical conductivity of dP3HT_DBSA obtained was 172 ± 5.21 S cm⁻¹ which is the highest value relative to previously reported.

Materials diversity of hydrogel: Synthesis, polymerization process and soil conditioning properties in agricultural field

BACKGROUND

The cumulative influence of global warming, climate abrupt changes, growing population, topsoil erosion is becoming a threatening alarm for facing food challenges and upcoming global water issues. It ultimately affects the production of food in a water-stressed environment and slows down the production with more consumption of fertilizers by plants. The superabsorbent hydrogels (SAHs) have extensive applications in the agricultural field and proved very beneficial for plant growth and soil health. These polymeric materials are remarkably distinct from hygroscopic materials owing to their multidimensional network structure. It retains a lot of water in its 3D network and releases it slowly along with nutrients to plant in stressed environment.

AIM OF REVIEW

A soil conditioner boosts up the topology, compactness, and mechanical properties (swelling, water retention, and slow nutrient release) of soil. The superabsorbent hydrogel plays an astonishing role in preventing the loss of nutrients during the heavy flow of rainwater from the upper surface of soil because these SAHs absorb water and get swollen to keep water for longer time. The SAHs facilitate the growth of plants with limited use of water and fertilizers. Beyond, it improves the soil health and makes it fertile in horticulture and drought areas.

KEY SCIENTIFIC CONCEPT OF REVIEW

The SAHs can be synthesized through grafting and cross-linking polymerization to introduce value-added features and extended network structure. The structure of superabsorbent hydrogel entirely based on cross-linking that prompts its use in the agricultural field as a soil conditioner. The properties of a SAHs vary due to its nature of constituents, polymerization process (grafting or cross-linking), and other parameters. The use of SAHs in agricultural field comparatively enhances the swelling rate up to 60-80%, maximum water retaining, and slowly nutrient release to plants for a longer time.

Doped Poly(3-hexylthiophene) Coatings onto Chitosan: A Novel Approach for Developing a Bio-Based Flexible Electronic

Conductive and flexible bio-based materials consisting of chitosan films coated with conductive poly(3-hexylthiophene) (P3HT) were prepared. Thermal, optical, mechanical, morphological, wettability, and conductive properties were analyzed. In a very simple and effective method of chitosan film modification, a controlled volume of a P3HT solution was deposited onto a previously formed chitosan film, assisted by the spin coating method. Later, P3HT-coated chitosan films were doped by simple contact with an aqueous solution of HAuCl₄. The use of HAuCl₄ becomes attractive because the reports on the doping process in this type of material using this reagent are still scarce and recent to date. In addition, since this acid is a well-known metal nanoparticle precursor, its use opens new future perspectives for these materials into new applications. The effect of P3HT concentration and doping times on film properties was studied. Attenuated total reflectance spectroscopy and UV-Vis spectroscopy allowed us to demonstrate that the presence of the P3HT coating and its doping induce significant changes in the vibrational modes and optoelectronic properties of samples. Additionally, the images obtained by scanning electron microscopy showed a well-distributed and homogeneous coating on the surface of chitosan films. Measured conductivity values of doped film samples fall in the range from 821.3 to 2017.4 S/m, representing, to the best of our knowledge, the highest values reported in the literature for chitosan/chitin-based materials. Indeed, these values are around or even higher than those obtained for some materials purely consisting of conductive polymers.

Functionalized Cellulose Nanocrystal-Mediated Conjugated Polymer Aggregation

Inducing the self-assembly of π-conjugated polymers into semicrystalline aggregates has been a topic of substantial interest in the field of organic electronics and is typically achieved using energy-intensive solution processing or postfilm deposition methods. Here, we demonstrate the ability of bioderived cellulose nanocrystals (CNCs) to act as structure-directing agents for the conjugated semiconducting polymer, poly(3-hexylthiophene) (P3HT). CNCs were grafted with polystyrene, P3HT or poly(N-isopropylacrylamide), and subsequently blended with P3HT in solution to study the effect on conjugated polymer self-assembly. The presence of polymer-grafted CNCs resulted in an increase in P3HT semicrystalline aggregate formation, the degree of which depended on the surface free energy of the grafted polymer. The time-dependent P3HT aggregation was characterized by UV-vis spectroscopy, and the resulting data was fit to the Avrami crystallization model. The surface energies of each additive were calculated via contact angle measurements and were used to elucidate the mechanism of P3HT aggregation in these blended systems. P3HT aggregation was enhanced by unfavorable polymer-polymer interactions at the CNC surface, and spatial confinement effects that were imposed by phase separation. Finally, films were cast from the P3HT/CNC solutions and their electronic performance was characterized by organic field-effect transistor device measurements. Films containing polymer-grafted CNCs exhibited higher charge-carrier mobilities, in some cases, up to a 6-fold increase. These bioderived particles constituted a significant volume fraction of the deposited P3HT thin films with an increase in performance, showing promise as a method for reducing costs and improving the sustainability of organic electronics.

Flexible electrically conductive films based on nanofibrillated cellulose and polythiophene prepared via oxidative polymerization

Industrial ecology, sustainable manufacturing, and green chemistry have been considered platform-based approaches to the reduction of the environmental footprint. Recently, nanofibrillated cellulose (NFC) has gained significant interest due to its mechanical properties, biodegradability, and availability. These outstanding properties of NFC have encouraged the development of a more sustainable substrate for electronics. In this context, the combination of NFC and conductive polymers may create a new class of biocomposites to be used in place of conventional electronics which are not optimally designed for use in flexible and mechanically robust devices. In this study, polythiophene was grafted onto nanocellulose surface at appropriate reaction times to obtain a strong, flexible, foldable films with capacity for electrical conductivity. Nanocomposites films were synthesized by a one-step reaction in which a 3-methyl thiophene monomer was oxidatively polymerized onto nanocellulose backbone. The nature of the fabricated NFC films changed from insulator to semiconductor material upon oxidative polymerization.

Enhanced mechanical properties of bacterial cellulose nanocomposites produced by co-culturing Gluconacetobacter hansenii and Escherichia coli under static conditions

Including additives in the culture media during bacterial cellulose (BC) biosynthesis is a traditional method to produce BC-based nanocomposites. This study examines a novel fermentation process, which is to co-culture Gluconacetobacter hansenii (G. hansenii) with Escherichia coli (E. coli) under static conditions, to produce BC pellicles with enhanced mechanical properties. The mannose-rich exopolysaccharides (EPS) synthesized by E. coli were incorporated into the BC network and affected the aggregation of co-crystallized microfibrils without significantly changing the crystal sizes of BC. When co-culturing G. hansenii ATCC 23769 with E. coli ATCC 700728, which produced a low concentration of EPS at 3.3 ± 0.7 mg/L, the BC pellicles exhibited a Young's modulus of 4,874 ± 1144 MPa and a stress at break of 80.7 ± 21.1 MPa, which are 81.9% and 79.3% higher than those of pure BC, respectively. The growth dynamics of the two co-cultured strains suggested that the production of BC and EPS were enhanced through co-culturing fermentation.

Chemotherapy of Breast Cancer Cells Using Novel pH-Responsive Cellulose-Based Nanocomposites

Purpose: The objective of the current study was to compare the anticancer efficacy of doxorubicin-loaded cellulose based magnetic (Fe3O4), zinc oxide (ZnO) nanoparticles on and free doxorubicin (DOX) on MCF-7 breast cancer cells. Methods: Novel pH-sensitive cellulose-graft poly acrylic acid based Fe3O4 (Cellulose-g-PAAg- PAcMNPs) and ZnO (Cellulose-g-PAA-g-PAcZnO) nanocomposites were synthesized via polymerization of acrylic acid and modified 3-(trimethoxysilyl) propyl methacrylate onto the cellulosic backbone via reversible addition-fragmentation chain transfer (RAFT) method. Results : Cellulose-g-PAA-g-PAcMNPs and Cellulose-g-PAA-g-PAcZnO nanocarriers with mean diameter of 15 and 38 nm were prepared successfully. DOX was loaded effectively to the ZnO and Fe3O4 nanocarriers via complexing and electrostatic force with great encapsulation efficiency of 99.07% and 98.92%, respectively. DOX-loaded nanocarriers showed obvious pHdependent tumor specific drug release pattern. MTT assay results indicated that IC50 of the DOX loaded Cellulose-g-PAA-g-PAcZnO, DOX loaded Cellulose-g-PAA-g-PAcMNPs and free DOX after 48 hours treatment with MCF7 cell lines were about 24.03, 49.27 and 99.76 μg mL-1, respectively. Therefore both DOX nanoformulations significantly increase antitumor ability compared to free DOX (P < 0.05). The results of MTT assay and DAPI staining revealed that DOX-loaded Cellulose-g-PAA-g-PAcZnO NPs show higher chemotherapy efficiency in MCF7 breast cancer cell line compare to the DOX-loaded Cellulose-g-PAA-g-PAcMNPs due to high interaction of ZnO with DOX. Conclusion: The formation of the complexes between the DOX and ZnO nanoparticles at the chelating sites of the quinone and the phenolic oxygen molecules of DOX, lead to more sustained drug release and enhanced chemotherapy effectiveness by increasing the intracellular concentration of DOX.

Fluorescence control of chitin and chitosan fabricatedviasurface functionalization using direct oxidative polymerization

The copolymer of 3-hexylthiophene (3HT) and fluorene (F) was directly grafted onto chitin and chitosan using FeCl₃ as an oxidant. The properties of the grafted chitin/chitosan were characterized by Fourier transform infrared (FT-IR) spectroscopy, UV-Vis spectroscopy, fluorescence spectroscopy, X-ray diffraction analysis, thermogravimetric analysis (TGA), transmission electron microscopy-energy dispersive X-ray spectroscopy, and quantum yield measurements. The UV-Vis absorption peaks of the chitin/chitosan grafted with 3-hexylthiophene and fluorene copolymer were increasingly blue-shifted upon increasing the fluorene content and the red-shifted emission of the grafted chitin/chitosan were controlled by varying the monomers feed of the 3HT/F units. The hypsochromic and bathochromic shifts of chitin/chitosan were ascribed to the (3HT/F) moieties grafted to their surface. The quantum yield of grafted chitin/chitosan increased upon increasing the fluorene content. The TGA and XRD analysis revealed that the thermal stability and crystallinity of chitin/chitosan decreased upon grafting the copolymer of fluorene and 3-hexylthiophene. This article represents a simple route towards the surface modification of chitin and chitosan using conducting copolymers, providing multicolor chitin and chitosan via a one-step reaction.

The copolymer of 3-hexylthiophene (3HT) and fluorene (F) was directly grafted onto chitin and chitosan using FeCl₃ as an oxidant.