Polymer Films Research Articles

Drug polymer conjugates: Average release time from thin films

The reaction–diffusion problem describing the release of drugs conjugated through labile bonds to polymeric thin films has a known analytical solution, when the reaction kinetics is of first order. Using this solution, an exact formula is derived for the average release time of the system. This simple expression provides the characteristic time of release tav as the sum of the corresponding average diffusion time plus the inverse reaction rate constant: tav=(1/12)⋅(L2/D)+(1/k), where L is the slab thickness, D the diffusion coefficient, and k the reaction rate constant. The former term dominates in a diffusion-controlled release, while the latter one in a reaction-controlled delivery. The crossover regime is exactly described by their sum. The obtained result for the average release time is verified by direct numerical integration through the drug release profiles of the analytical solution. The value of fractional drug release at the characteristic average time is between 60–64%. These results can be used for the design of polymer-drug conjugates with a desired delivery time scale, as well as for the experimental determination of the values of microscopic parameters D and k in a conjugated system of interest.

Tailoring the Density of State of n-Type Conjugated Polymers through Solvent Engineering for Organic Electrochemical Transistors.

Conjugated polymers with ethylene glycol-type side chains are commonly used as channel materials in organic electrochemical transistors (OECTs). To improve the performance of these materials, new chemical structures are often created through synthetic routines. Herein, we demonstrate that the OECT performance of these polymers can also be improved by changing their density-of-state (DOS) profile through solvent engineering. Depending on the solvent polarity, it solvates the backbone and side chains of the conjugated polymer differently, leading to differences in molecule orientation, π-stacking paracrystallinity, and film defects, such as grain boundaries and pinholes. This then results in a change in the DOS profile of the polymer. A more intense and narrow-width DOS distribution is usually observed in organic films with an "edge on" orientation and fewer film defects, while films with a "face on" orientation and apparent defects show a broadened DOS profile. The OECT devices that use the polymer film with a more intense and narrow-width DOS profile exhibit a better-normalized transconductance and figure-of-merit μC* than those with a broadened DOS profile (0.74 to 4.29 S cm-1 and 3.5 to 14.3 F cm-1 V-1 s-1). This study provides useful insights into how the DOS profile affects the mixed ionic-electronic conduction performance and presents a new avenue for improving n-type OECT materials.

Passively harmonic mode-locked GHz U-band femtosecond pulse generation based on soliton self-frequency shift

We demonstrate a GHz U-band fiber laser harnessing soliton self-frequency shift (SSFS). The seed source is a passively harmonic mode-locked (HML) fiber laser based on carbon nanotubes (CNTs) polymer film. By adjusting the pump power and polarization controller (PC) appropriately, the repetition rate can be tuned up to 1.104 GHz with a side mode suppression ratio (SMSR) of 42.5 dB. The seed source with different repetition rates can be frequency shifted from C-band to U-band in a piece of dispersion-shifted fiber (DSF) after amplification. We selected three repetition rates (457.8 MHz, 700.1 MHz, and 1104.1 MHz) and systematically studied the impact of different repetition rates on SSFS. The broad tuning range of wavelengths covering the entire U-band can be obtained by adjusting the pump power of the main amplifier. To the best of our knowledge, the demonstrated laser is the first U-band femtosecond fiber laser based on passively HML with a repetition rate over 1 GHz.

Artemisia monosperma essential oil nanoformulations alleviate imiquimod-induced psoriasis-like dermatitis in mice

Psoriasis is an inflammatory immune-mediated skin disease that affects nearly 2–3 % of the global population. The current study aimed to develop safe and efficient anti-psoriatic nanoformulations from Artemisia monosperma essential oil (EO). EO was extracted using hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and head-space solid-phase microextraction (HS–SPME), as well as GC/ MS was used for its analysis. EO nanoemulsion (NE) was prepared using the phase inversion method, while the biodegradable polymeric film (BF) was prepared using the solvent casting technique. A.monosperma EO contains a high percentage of non-oxygenated compounds, being 90.45 (HD), 82.62 (MADH), and 95.17 (HS–SPME). Acenaphthene represents the major aromatic hydrocarbon in HD (39.14 %) and MADH (48.60 %), while sabinene as monoterpene hydrocarbon (44.2 %) is the primary compound in the case of HS–SPME. The anti-psoriatic Effect of NE and BF on the successful delivery of A.monosperma EO was studied using the imiquimod (IMQ)-induced psoriatic model in mice. Five groups (n = 6 mice) were classified into control group, IMQ group, IMQ+standard group, IMQ+NE group, and IMQ+BF group. NE and BF significantly alleviated the psoriatic skin lesions and decreased the psoriasis area severity index, Baker’s score, and spleen index. Also, they reduced the expression of Ki67 and attenuated the levels of tumor necrosis factor-alpha, interleukin 6, and interleukin 17. Additionally, NE and NF were able to downregulate the NF-κB and GSK-3β signaling pathways. Despite the healing properties of BF, NE showed a more prominent effect on treating the psoriatic model, which could be referred to as its high skin penetration ability and absorption. These results potentially contribute to documenting experimental and theoretical evidence for the clinical uses of A.monosperma EO nanoformulations for treating psoriasis.

Structural, morphological and functional properties of films polymer analogues of (co)polyvinylsuccinates

The results of a study of the structural features and associated physicochemical characteristics of films based on copolymers of n-butyl acrylate with N-vinylsuccinamic acid (sodium salt), including those containing bioactive substances (BAS), and their influence on the duration of BAS release depending on chemical structure and composition of the copolymer, film formation conditions, the nature of the introduced BAS, contact medium and release of BAS are presented.

The effect of dexamethasone addition to gentamicin polymeric films of hydroxypropyl methylcellulose/chitosan and hydroxypropyl methylcellulose/polyvinylpyrrolidone

AbstractMany polymeric film formulas containing antibiotics failed in preventing microbial infections due to microbial resistance. One of the main reasons for microbial resistance is the formation of biofilm layers which prevent the drug from reaching the active site. This study aims to evaluate the effect of dexamethasone addition to polymeric film formula containing gentamicin. The polymeric formula containing both dexamethasone and gentamicin were characterized in terms of film's diameters, content uniformity, moisture content, matrix‐drugs association, and drug release. Antibiofilm and antimicrobial activity were used to evaluate polymeric formula containing drug. The addition of dexamethasone to the polymeric formula revealed that most of dexamethasone released and diffused in the first 300 min, while gentamicin release and diffusion had a slower rate like the release of gentamicin from formulations without dexamethasone. The addition of dexamethasone resulted in improved antibiofilm and antibacterial activity with the lowest antibiofilm activity >96% and antibacterial activity >87%. Therefore, dexamethasone addition to polymeric formula containing gentamicin improved the biological activity without any effects on the film characteristics.Highlights Dexamethasone addition to polymeric formula containing gentamicin significantly improved the biological activity. Most of dexamethasone released and diffused in the first 300 min. The addition of dexamethasone resulted in the lowest antibiofilm activity of gentamicin of >96% and antibacterial activity >87%.

Process dependent properties of glassy polymer films revealed by molecular dynamics simulations

A molecular dynamics (MD) framework has been proposed to systematically simulate process (but not cooling rate) dependent properties of glassy polymer films. With the coarse-grained (CG) polylactide (PLA) of low molecular weight (MW), the simulated thermal properties of glassy films are confirmed to be surely decided by the routes to prepare them. While the glassy films initially prepared from the melt bulk are stable, the glassy film initially constructed from the glassy bulk appears to be unstable, featuring highest potential energy among those films and different averaged heat capacity from the bulk counterparts. Inspired by physical vapour deposition (PVD), a surface formation process is further applied to the unstable film to generate stable glassy polymer films. Similar to the PVD, an optimal temperature at which the film is most stable can be identified with lower potential energy than the conventional films, for which free surface and enhanced order of the middle layer are responsible. This work paves a way for obtaining simulated models of stable glassy films and experimentally preparing advanced glassy films for high MW polymers, which otherwise are hard to be realized by the PVD process.

Characterization of plasma polymerized acetonitrile film for fluorescence enhancement and its application to aptamer-based sandwich assay.

Among biosensing systems for sensitive diagnoses fluorescence enhancement techniques have attracted considerable attention. This study constructed a simple multilayered structure comprising a plane metal mirror coated with a plasma-polymerized film (PPF) as an optical interference layer on a glass slide for fluorescence enhancement. Plasma polymerization enables the easy deposition of organic thin films containing functional groups, such as amino groups. This study prepared PPFs using acetonitrile as a monomer, and the influences of washing and the output powers of plasma polymerization on PPF thickness were examined by Fourier transform infrared spectroscopy. This is because controlling the PPF thickness is vital in fluorescence enhancement. Multilayered glass slides prepared using a silver layer with 84 nm-thick acetonitrile PPFs exhibited 11- and 281-fold fluorescence enhancements compared with those obtained from the substrates with a bare surface and only modified by the silver layer, respectively. Oligonucleotides labeled with a thiol group and cyanine5 were successfully immobilized on the multilayered substrates, and the fluorescence of the acetonitrile PPFs was superior to that of the allylamine and cyclopropylamine PPFs. Furthermore, an aptamer-based sandwich assay targeting thrombin was performed on the multilayered glass slides, resulting in an approximately 5.1-fold fluorescence enhancement compared with that obtained from the substrate with a bare surface. Calibration curves revealed the relationship between fluorescence intensity and thrombin concentration of 10-1000 nM. This study demonstrates that PPFs can function as materials for fluorescence enhancement, immobilization for biomaterials, and aptamer-based sandwich assays.

Stretchable Iontronic Tactile Sensing Fabric.

The iontronic tactile sensing modality has garnered significant attention due to its exceptional sensitivity, immunity to noise, and versatility in materials. Recently, various formats of iontronic tactile sensors have been developed, including droplets, polymer films, paper, ionic gels, and fabrics. However, the stretchability of the current iontronic pressure sensing fabric is inadequate, hindered by the limited stretchiness of the ionic functional fabric. Incorporating a stretchable tactile sensing implement could enhance the wear comfortability by preventing relative movement and ensuring intimate contact between the sensor and the skin. The research focuses on the development of a stretchable iontronic pressure sensing (SIPS) fabric for monitoring diverse aspects of body health and movement in wearable applications. The tactile sensing structure is generated at the iontronic interface between highly stretchable ionic and conductive fabrics. In particular, the ionic fabric is prepared by coating a layer of polyurethane/ionic liquid gel onto a Spandex fabric. To showcase its remarkable sensitivity, stretchability, and ability to detect diverse body information, several application scenarios have been demonstrated including an elastic wristband for precise pulse wave detection, a flexible belt with multitactile sensing channels for respiration and motion tracking purposes, and a stretchable fabric cuff equipped with a high-resolution sensing array comprising 32 × 32 units for accurate gesture recognition.

Aloe vera Miller extract as a plasticizer agent to polymeric films: A structural and functional component

The pharmaceutical and cosmetic industries have found natural polysaccharides-based polymeric films helpful for the topical application of drugs. Plasticizers, such as glycerol, are added to achieve films' desired mechanical, elastic, and flexible properties. Aloe vera Miller mucilage is known for healing burns and wounds, relieving pain, and moisturizing, suggesting its great potential for managing multiple topical issues. Herein, we exploited the plasticizing potentialities of A. vera extract when combined with gellan or carrageenan polysaccharides to produce films. The extract of A. vera mucilage was prepared in propane-1,2-diol, and its composition was comparatively evaluated with a commercial extract using a chemometric method. Next, it was added to the films obtained using the solvent-casting method. The formulations were investigated regarding the mechanical properties, swelling, water loss, porosity, water vapor transmission rate, degree of occlusion, adhesion force, and antioxidant action. Fourier transform infrared spectroscopy assessed the films stability and homogeneity with an exploratory chemometric method to classify the samples. The results showed that carrageenan and gellan polysaccharides-based polymeric films have great potential for including A. vera extract. The extract acts as a plasticizer and promotes desirable properties and swelling behavior for films intending wound management. Comparatively, films prepared with glycerol beyond the extract presented higher thickness, lower swelling, and higher occlusion and antioxidant activity. Despite this, glycerol seems to negatively influence the homogeneity of the extract on the film surface. In addition, regarding polysaccharides, carrageenan showed higher bioadhesion. Therefore, the films produced exhibited favorable properties, highlighting their potential for further research regarding wound management.

One-step light-induced hierarchical surface wrinkles on photodegradable polymer films

Photodegradable polymers have become an emerging class of stimulus-sensitive materials for advanced applications, in which using the photolysis characteristic for patterning surface is a key but still a notable challenge. Herein, we report a simple, facile, green and high-efficiency strategy to induce and further tune surface wrinkling only relying on one-step ultraviolet (UV) irradiation of a photodegradable polymer-based film/substrate composite system. Interestingly, a series of intriguing wrinkling states from no wrinkling to surface wrinkling and final no wrinkling with UV exposure take place on the photodegradable polymer film. This wrinkling behavior is intimately related to the competition between the stress accumulation from the heating effect of UV lamp itself and the stress release from the UV-induced molecular chain breakage. Meanwhile, the dependence of photodegradable polymer film modulus and photodegradation-induced stress release on the exposure time has been characterized by taking advantage of surface wrinkling metrology, which is not easily accessible to other systems and methods. This one-step light irradiation strategy has enabled the fabrication of diverse hierarchical surface wrinkling on photodegradable polymer film by simply controlling the UV exposure time. As demonstrated, these hierarchical surface wrinkles with tunable features have been applied for optical information display/storage and optical gratings. Notably, this simple flexible light control strategy not only provides new insights into the photo-induced change in mechanical properties and stress release of photodegradable polymers in molecular level, but also paves new avenues for advanced wrinkle-based applications by incorporating desirable functional materials into the photodegradable polymer-based systems.

Rational Design of Fluorinated 2D Polymer Film Based on Donor-Accepter Architecture toward Multilevel Memory Device for Neuromorphic Computing.

Fluorine-containing 2D polymer (F-2DP) film is a desired system to regulate the charge transport in organic electronics but rather rarely reports due to the limited fluorine-containing building blocks and difficulties in synthesis. Herein, a novel polar molecule with antiparallel columnar stacking is synthesized and further embedded into an F-2DP system to control over the crystallinity of F-2DP film through self-complementary π-electronic forces. The donor-accepter-accepter'-donor' (D-A-A'-D') structure regulates the charge transportation efficiently, inducing multilevel memory behavior through stepwise charge capture and transfer processes. Thus, the device exhibits ternary memory behavior with low threshold voltage (Vth1 of 1.1V, Vth2 of 2.0V), clearly distinguishable resistance states (1:102:104) and ternary yield (83%). Furthermore, the stepwise formation of the charge complex endows the device with a wider range to regulate the conductive state, which allows its application in brain-inspired neuromorphic computing. Modified National Institute of Standards and Technology recognition can reach an accuracy of 86%, showing great potential in neuromorphic computing applications in the post-Moore era.

Long-Term Culture of Human Pluripotent Stem Cells in Xeno-Free Condition Using Functional Polymer Films.

Human pluripotent stem cells (hPSCs), encompassing human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), hold immense potential in regenerative medicine, offering new opportunities for personalized cell therapies. However, their clinical translation is hindered by the inevitable reliance on xenogeneic components in culture environments. This study addresses this challenge by engineering a fully synthetic, xeno-free culture substrate, whose surface composition is tailored systematically for xeno-free culture of hPSCs. A functional polymer surface, pGC2 (poly(glycidyl methacrylate-grafting-guanidine-co-carboxylic acrylate)), offers excellent cell-adhesive properties as well as non-cytotoxicity, enabling robust hESCs and hiPSCs growth while presenting cost-competitiveness and scalability over Matrigel. This investigation includes comprehensive evaluations of pGC2 across diverse experimental conditions, demonstrating its wide adaptability with various pluripotent stem cell lines, culture media, and substrates. Crucially, pGC2 supports long-term hESCs and hiPSCs expansion, up to ten passages without compromising their stemness and pluripotency. Notably, this study is the first to confirm an identical proteomic profile after ten passages of xeno-free cultivation of hiPSCs on a polymeric substrate compared to Matrigel. The innovative substrate bridges the gap between laboratory research and clinical translation, offering a new promising avenue for advancing stem cell-based therapies.

Sexual hormones monitoring in surface waters and wastewaters from Northern Italy by thin film microextraction coupled with HPLC-MS/MS.

The occurrence of sex steroid hormones, viz. oestrogens and progestins, in aquatic ecosystems is of global concern due to their role as endocrine disrupting chemicals, even at low concentration (μg L-1 or less). Thus, it is essential to monitor these organic pollutants to get a realistic picture of their presence and to control their contamination levels in environmental water bodies. In this respect, we have explored the use of self-prepared polymeric films as novel sorptive phase for the microextraction of 17β-estradiol, 17α-ethinylestradiol, estrone, progesterone, medroxyprogesterone acetate and hydroxyprogesterone. The thin film microextraction procedure has been developed, evaluating different film compositions, sample volumes and elution conditions to recover the sorbed analytes. The overall method provides good reproducibility (RSD < 12%) and recoveries higher than 60%. The final method has been applied to environmental monitoring in surface waters (river and lake samples) and urban wastewater treatment plant effluents and influents from Northern Italy, to get a contamination snapshot of this highly urbanized area.

A Study on Formulation and Assessment of Heart Rate Lowering Agent Ivabradine Orally Tablets

This study aimed to develop a method for quantifying the amount of ivabradine in films that are ingested and administered with ease. To do this, a dry granulation technique was applied. The dry granulation process yielded good results when the F5 formulation was mixed with starch, anhydrous lactose, and microcrystalline cellulose PH 102. The strength of the tablet was modified by adding croscarmellose sodium. Sodium starch glycolate was used as the dissolving agent. Purified talc and colloidal silicon dioxide were utilised as glidents. In this mixture, magnesium stearate was employed as a lubricant. Purified talc was used to make tablets stronger and smoother, and titanium dioxide was used to make films opaque. Hydroxypropyl Methyl Cellulose 6 CPS was utilised as a film-forming agent, and polyethylene glycol 6000 was employed as a plasticizer. The manufactured tablet formulations were examined for friability (%), thickness, hardness, and disintegration time in addition to other medicinal properties. It was observed that the drug content was 99.94% and the in-vitro dissolution percentage was measured as 99.89%. Tablets coated with polymer film were manufactured by dry granulation. Ivabradine is administered to persons with coronary artery disease who have normal sinus rhythm and a heart rate more than 72 bpm in order to treat the symptoms of chronic stable angina pectoris. For the symptomatic treatment of stable angina pectorals and symptomatic eternal heart failure, ivabradine is a medication that reduces pulse rate.

Enhancing the Kinetics of Vapor-based Polymerization by Pulsed Filament Approach.

Initiated chemical vapor deposition is a versatile technique for synthesizing conformal polymer films on both planar and porous surfaces. It can retain functional groups and avoid undesired cross-linking. However, there is still room for enhancing its performance without altering the feed parameters. Here, we investigate a pulsed iCVD approach to improve the deposition process, achieved by switching on and off the resistively heated filament periodically. By strategically switching off the filament, a shortage of thermally activated primary radicals was created, which allowed uninterrupted chain propagation with fewer termination reactions and potentially increased monomer conversion rates. This has caused significantly faster deposition kinetics with a higher molecular weight and longer chain length for poly(glycidyl methacrylate) compared to continuous deposition. Spectra analyses confirmed that the functionality and stoichiometry ratios remained intact throughout the pulsed deposition process. The pulsed iCVD method is therefore a competitive and sustainable tool, demonstrating fast deposition kinetics and a well-preserved functionality.

Monitoring the curing, degradation and moisture ingress into alkyl 2-cyanoacrylate adhesives using electrochemical impedance spectroscopy

AbstractElectrochemical impedance spectroscopy (EIS) was employed in an attempt to gain insight into the mechanisms of ethyl 2-cyanoacrylate (ECA) curing (polymerisation) and bonding on aluminium alloy 2024 metal. EIS can detect ionic movement, adsorption processes, charge transfer and storage occurring at an adhesive/substrate interface and/or in a bulk bond line during curing. Low-frequency capacitance measurements demonstrated sensitivity to surface polymerisation reactions and were modelled using an equivalent circuit model with two time constants in series. At a frequency of 1 kHz, changes in the dielectric polymer could be readily followed with time, confirmed by employing a crown ether to accelerate the polymerisation process. Hydrolytic degradation of poly-ECA bonds at a stainless steel interface was also investigated. An equivalent circuit model containing a number of circuit components comprising pore, charge transfer and diffusional impedances, along with polymer film, double layer and diffusional capacitances (represented by constant phase elements), was developed. Three regions were identified in the frequency domain and ascribed to processes taking place at the polymer/electrolyte and polymer/metal oxide interfaces. In short, EIS can be employed to follow the rate of polymerisation of ethyl-2-cyanoacrylate and also the degradation of the resulting polymer in saline solution.

Ultraviolet color image sensor based on CsPbBr3 inorganic perovskite nanocrystal film.

Ultraviolet and color imaging require different image sensors and optical channels, which results in large size, complex structure, and high cost of imaging systems. Here, we report a novel, to the best of our knowledge, image sensor that combines ultraviolet and color imaging functions. The fabrication of this image sensor is achieved by coating high-transparency CsPbBr3 perovskite nanocrystals in a polymer film on the color filter layer of a silicon-based detector. The film, serving as an ultraviolet photoluminescent layer, exhibits high transparency, exceeding 91.5% at wavelengths beyond the photoluminescence peak of 513 nm. During ultraviolet imaging, the film converts ultraviolet light into visible light, which passes through the green filter layer to reach the detector for imaging. During visible light imaging, red light, green light, and most of the blue light pass through the CsPbBr3 perovskite nanocrystal film and color filter layer to reach the detector for imaging. As a result, the image sensor can capture both 257 nm solar-blind ultraviolet images and color photos in the visible light.

Comparative efficacy of citric acid/tartaric acid/malic acid additive-based polyvinyl alcohol-starch composite films

To ascertain upon the ideal configuration of physico-mechanical qualities, efficient processing techniques, and network stability of the prepared bio-composite films in real-world applications, the polymeric materials shall be subjected to a careful manipulation. Such bio-composite films have outstanding combinations of biocompatibility and toxicity-associated safety qualities. Such research interventions will be beneficial for the packaging, pharmaceutical, and biomedical industries that wish to target and adopt them for commercial applications. In this article, three alternate organic acids, i.e., citric acid (CA), tartaric acid (TA), and malic acid (MA), are blended separately into polyvinyl alcohol (PVA)-starch (St)-glycerol (Gl) composite films and for the targeted purpose of enhanced crosslinking, plasticizing, and antibacterial capability of the polymer network. The organic acid-based bio-composite polymeric films were assessed in terms of swelling index (SI), in vitro degradation, tensile strength (TS), percentage elongation (%E), antibacterial activity, and cytotoxicity attributes. Among these, the MA-based PVA composite films outperformed the CA-based PVA composite film in terms of absorbency (SI 739.29%), mechanical strength (TS 4.88 MPa), and elasticity (%E 103.68%). Furthermore, following a 24-h incubation period, the MA-based films exhibited the highest proliferative effect of 215.59% for the HEK cells. In conclusion, the MA has been inferred to be the most relevant organic acid for the desired optimality of film composition, physical and biological properties, and cost.

Measurement of the depth-dependent local dynamics in thin polymer films through rejuvenation of ultrastable glasses

The depth dependence of structural relaxation dynamics is a key part of understanding thin glassy films. Despite this importance and decades of research, a method to provide this information has proved elusive. We measure the isothermal rejuvenation of stable glass films of poly(styrene), and demonstrate that the propagation of the front responsible for the transformation to a supercooled-liquid state serves as a highly localized probe of the local dynamics of the supercooled liquid. We use this connection to probe the depth-dependent relaxation rate with nanometric precision for a series of polystyrene films over a range of temperatures near the bulk glass transition temperature. The analysis shows the spatial extent of enhanced surface mobility and reveals the existence of an unexpected large dynamical length scale in the system. The results are compared with the cooperative-string model for glassy dynamics. The data reveals that the film-thickness dependence of whole film properties arises mainly from the volume fraction of the near-surface region. While the dynamics farthest from the free surface shows the expected bulk-like temperature dependence, the dynamics in the near-surface region shows very little dependence on temperature. This technique can be used in a broad range of thin film materials to gain previously unattainable information about localized structural relaxation.