Free-standing Polymeric Films Research Articles

Facile conversion of water to functional molecules and cross-linked polymeric films with efficient clusteroluminescence

Exploring approaches to utilize abundant water to synthesize functional molecules and polymers with efficient clusteroluminescence properties is highly significant but has yet to be reported. Herein, a chemistry of water and alkyne is developed. The synthesized products are proven as nonaromatic clusteroluminogens that could emit visible light. Their emission colors and luminescent efficiency could be adjusted by manipulating through-space interaction using different starting materials. Besides, the free-standing polymeric films with much high photoluminescence quantum yields (up to 45.7%) are in situ generated via a water-involved interfacial polymerization. The interfacial polymerization-enhanced emission of the polymeric films is observed, where the emission red-shifts and efficiency increases when the polymerization time is prolonged. The synthesized polymeric film is also verified as a Janus film. It exhibits a vapor-triggered reversible mechanical response which could be applied as a smart actuator. Thus, this work develops a method to synthesize clusteroluminogens using water, builds a clear structure-property relationship of clusteroluminogens, and provides a strategy to in situ construct functional water-based polymeric films.

Transmitting biomolecular chirality into carbon nanodots: a facile approach to acquire chiral light emission at the nanoscale.

Since the observation of chirality at the nanoscale, research focused towards the design and synthesis of optically active nanomaterials has been at a brisk pace. In this regard, carbon based zero dimensional nanomaterials have attracted vast attention due to their rich optical properties, abundance of raw materials, minimal environmental hazardousness, good solubility, and ease of surface modification. However, efforts focused towards the synthesis of chiral carbon nanodots exhibiting optical activity both in their ground and excited states are rather scarce. Herein, we report a facile synthetic approach for the preparation of three sets of intrinsically chiral carbon nanodots that exhibit intense circularly polarized luminescence. Synthesis under optimized conditions using l- and d-isomers of the chiral precursors led to the formation of carbon nanodots that displayed mirror image circular dichroism and circularly polarized luminescence signals revealing their ground and excited state chirality. The experimental results are supportive of the reported core-shell model comprising an achiral carbon core that is enclosed within an amorphous shell contributing to the chiral luminescence. The luminescence anisotropy and wavelength could be tuned by varying the experimental conditions such as temperature and pH. The chiral emissive properties of the nanoparticles could be demonstrated in free-standing polymeric films revealing their potential to be used as chiral light emitting agents in optical devices, data storage and security tags. Being the first observation of intrinsic circularly polarized luminescence from a range of carbon nanodots, both in the solution and solid state, we envisage that the work will open new avenues for the investigation of excited stated chirality at the nanoscale.

Spherical Confinement of Chromonics: Effects of a Chiral Aminoacid.

Induced or spontaneous chirality in natural systems is an intriguing issue. In recent years, a lot of attention has been focused on chirality of chromonic liquid crystals, a class of materials that is able to self-assemble in columnar structures. However, the mechanism involved in the arising of chirality in these materials, that starts at the molecular level and controls the supramolecular structure, is poorly understood; however, it is certainly affected by ionic strength. In this work we present the results obtained doping Cromolyn, a chromonic material, with a strong helical-twisting-power peptide, and confining it in a spherical geometry. We demonstrate, by means of optical polarized microscopy and structural analysis, that both the geometrical constraint and the presence of the chiral dopant enhance the chiral effect; we also demonstrate that they favor the rise of a highly ordered helical superstructure, that may be optimized upon adding an ionic dye to the system. Finally, we report a procedure for the preparation of free-standing polymeric films, embedding and preserving the microspheres, and paving the way for the creation of biocompatible and eco-friendly optical devices to be used in the sensor and anticounterfeiting fields.

Clean synthesis and characterization of green nanostructured polymeric thin films from endogenous Mg (II) ions coordinated methylolated-Cashew nutshell liquid

Abstract Efficient utilization of renewable feedstocks has been considered pivotal in sustainable development, controlling global warming, and as an alternative to petrochemical precursors. Here, we have presented a facile one-pot synthesis method for the fabrication of bacterial resistant, free-standing polymeric films and coatings by utilizing agro-waste based precursor material. The conversion of cashew nut shell liquid (CNSL) into a value-added product for this application was achieved through coordination of methylolated-CNSL and Mg (II) ions (Mg(II)CNSL). The resulting metal-organic framework (MOF) was then cured by following a greener approach with zero toxic/residue production through reacting Mg(II)CNSL with aliphatic amine [Mg(II)CNSL-FA]. The formulation mechanism of nanostructured Mg(II)CNSL-FA via the ring-opening reaction of benzoxazine, its polymerization with hydroxyl groups in CNSL, and coordination of Mg(II) ions were elucidated by FTIR, ATR, XRD, SEM/TEM, and DSC studies. The performance (flexibility, swelling behaviour, and water contact angle values), morphology, and thermal stability of Mg(II)CNSL-FA films were also compared (virgin ligand, CNSL-FA). The potential application of the film as an antibacterial material has been further tested against various bacterial strains (E.coli, P. aeruginosa, S. aureus, and B. subtilis). Overall, the research work is expected to broaden the utilization of CNSL, an agro-waste via cleaner production of flexible, free-standing, metal ions coordinated antibacterial film with possible application in surface coatings, adsorption, and water purification.

Film Impact Performance and Adhesion Study in Multilayered Systems

Abstract In this work we present a non-conventional approach to evaluate impact performance of polymeric films under a wide range of strain conditions by using a high-throughput mechanical testing (HTMECH) technique. The objective of this paper is to demonstrate how HTMECH can be employed to assess property–performance relationships in freestanding polymeric films and multilayered systems which are not possible to measure by following standard methodologies. Two main studies will be discussed: (1) toughness of freestanding thin films under high strain conditions, and (2) layer to layer adhesion in multilayer systems. In each case, mechanical properties such as critical strength and absorbed deformation energy were found to be correlated to different failure mechanisms and to thermal mechanical behavior of polymeric films.

Synergistic Action of Alginate Chemical Reduction and Laser Irradiation for the Formation of Au Nanoparticles with Controlled Dimensions

Freestanding natural polymeric films with homogeneous dispersion of gold nanoparticles (Au NPs) are obtained via in situ reduction of gold(III) chloride trihydrate by sodium alginate (SA) biopolymer matrix, during water evaporation without the use of additional reducing agents. The size and size distribution of the prepared Au NPs can be tuned by changing the concentration of the precursor and/or the procedure of the films’ preparation. The nanocomposite films after preparation are stable in ambient conditions and can be used without the need of further processing, or can be redissolved in water. In the case of water dissolution, the aqueous solutions are irradiated with UV laser pulses turning the previously formed Au NPs into smaller ones with narrow size distributions through photofragmentation. This technique is proposed as a green way of synthesizing Au NPs of tunable size in aqueous solution of alginate, or incorporated in alginate freestanding polymeric films, that due to their biocompatibility can be used as passive labels or active sensors in biomedical applications.

Design and Synthesis of Heterobimetallic Ru(II)–Ln(III) Complexes as Chemodosimetric Ensembles for the Detection of Biogenic Amine Odorants

The detection of neutral biogenic amines plays a crucial role in food safety. Three new heterobimetallic Ru(II)-Ln(III) donor-acceptor complexes, KPrRu, KNdRu, and KSmRu, K{[Ru((II))((t)Bubpy)(CN)4]2-Ln((III))(H2O)4} (where (t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine), have been synthesized and characterized. Their photophysical and X-ray crystallographic data were reported in this study. These complexes were found to be selective for biogenic amine vapors, such as histamine, putrescine, and spermidine, with a detection limit down to the ppb level. The sensitivities of these complexes to the amines were recorded as ~log K = 3.6-5.0. Submicron rods of the complexes, with a nanoscale diameter and microscale length, were obtained through a simple precipitation process. Free-standing polymeric films with different degrees of porosity were fabricated by blending the submicron rods with polystyrene polymer. The polymer with the highest level of porosity exhibited the strongest luminescence enhancement after amine exposure. Real time monitoring of gaseous biogenic amines was applied to real fish samples (Atlantic mackerel) by studying the spectrofluorimetric responses of the Ru(II)-Ln(III) blended polymer film.

Synthesis, characterization and properties of poly-(3-methyldiphenylamine) and poly(3-methoxydiphenylamine)

The electrochemical oxidation of 3-methyldiphenylamine, 3-MeDPA, and 3-methoxydiphenylamine, 3-MeODPA, in lithium perchlorate CH 3CN solutions produced either thin, uniform polymeric films on ITO electrodes or high quality, free-standing polymeric films with good electrochemical response. Thin polymer films exhibited multiple colour changes (pale yellow-yellow-green-blue) when the potential was cycled between 0.0 and 1.2 V vs. Ag/AgCl in LiClO 4-CH 3CN. Degradation occurred during long term cycling tests between 0.0 and 1.2 V, and could be inhibited substantially by the addition of strong acids. The polymer films exhibited electrochromic properties when dipped in aqueous solutions at various pHs. The free-standing film of poly(3-methyldiphenylamine), poly(3-MeDPA), showed a highly porous, granular morphology, whereas a dense, fibrous morphology was observed for poly(3-methoxydiphenylamine), poly(3-MeODPA). These free standing films may be doped and undoped chemically by immersing in acid or alkaline media. The chemical oxidation of 3-MeDPA and 3-MeODPA in acetonitrile, using copper perchlorate as an oxidative coupling reagent, also gave polymers with high molecular masses and their IR spectra are similar to those obtained by electrochemical polymerization. The electrical conductivity measurements on pressed pellets and free standing films of poly(3-MeDPA) and poly(3-MeODPA) gave room temperature conductivities in the range of 10 −5 and 10 −6 S/cm, respectively.