Silicone-based Polymers Research Articles

Cross-Linked Luminescent Polymers Based on β-Diketone-Modified Polysiloxanes and Organoeuropiumsiloxanes.

Nowadays, luminescent materials attract wide attention due to their valuable characteristics and broad area of potential application. Luminescent silicone-based polymers possess unique properties, such as flexibility, hydrophobicity, thermal and chemical stabilities, etc., which allow them to be utilized in various fields, such as optoelectronics, solid-state lasers, luminescent solar concentrators, sensors, and others. In the present work, a metal-ligand interaction approach was applied to obtain new cross-linked luminescent polymers based on multiligand polysiloxanes with grafted β-diketone fragments and organoeuropiumsiloxanes containing various organic substituents. Organoeuropiumsiloxanes were utilized as a source of Eu3+ ions due to their compatibility with the silicon matrix. All synthesized polymers were fully characterized and their physicochemical, mechanical, self-healing, optical, and thermal properties were studied.

Conducting Silicone-Based Polymers and Their Application.

Over the past two decades, both fundamental and applied research in conducting polymers have grown rapidly. Conducting polymers (CPs) are unique due to their ease of synthesis, environmental stability, and simple doping/dedoping chemistry. Electrically conductive silicone polymers are the current state-of-the-art for, e.g., optoelectronic materials. The combination of inorganic elements and organic polymers leads to a highly electrically conductive composite with improved thermal stability. Silicone-based materials have a set of extremely interesting properties, i.e., very low surface energy, excellent gas and moisture permeability, good heat stability, low-temperature flexibility, and biocompatibility. The most effective parameters constructing the physical properties of CPs are conjugation length, degree of crystallinity, and intra- and inter-chain interactions. Conducting polymers, owing to their ease of synthesis, remarkable environmental stability, and high conductivity in the doped form, have remained thoroughly studied due to their varied applications in fields like biological activity, drug release systems, rechargeable batteries, and sensors. For this reason, this review provides an overview of organosilicon polymers that have been reported over the past two decades.

Silicone Polymers—Celebrating 80 Years of the Direct Process

Silicone Polymers—Celebrating 80 Years of the Direct Process

Synthesis and properties of UV-curable polyurethane acrylates with reactive silicones

Over the past few years, silicone-based polymers have been widely studied because silicone shows unique surface properties, such as hydrophobicity, film formability, etc and then silicone-based compounds are being mainly applied to the coating field. To have these characteristics in coatings, it is crucial that silicone component participates in covalent bonding. In this research, UV-curable polyurethane acrylates (PUAs) with different molecular weights and contents of reactive silicones were synthesized to improve the surface and mechanical properties of coating films. The synthesized PUAs were identified with FT-IR spectra and the mechanical properties of the cured PUAs films were investigated by UTM. The water contact angle of the cured PUAs was measured by the drop shape analyzer and the gloss values of PUAs were measured by a gloss meter. Finally, the optimum content of reactive silicones in the PUAs was obtained.

Pentadecanal and pentadecanoic acid coatings reduce biofilm formation of Staphylococcus epidermidis on PDMS

Staphylococcus epidermidis is well known to be one of the major causes of infections related to medical devices, mostly due to its strong capacity to form device-associated biofilms. Nowadays, these infections represent a severe burden to the public health system and the necessity of novel antibacterial strategies for the treatment of these difficult-to-eradicate infections is urgent. The Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 was found to be able to produce an anti-biofilm molecule, the pentadecanal, active against S. epidermidis. In this work, we modified one of the most widely used silicone-based polymers, polydimethylsiloxane (PDMS), by adsorption of pentadecanal and its most promising derivative, pentadecanoic acid, on the PDMS surface. The biofilm formation of S. epidermidis RP62A on both untreated and modified PDMS was performed in a parallel plate flow chamber system, demonstrating the capability of the proposed anti-biofilm coatings to strongly reduce the biofilm formation. Furthermore, drug-release capacity and long-term efficacy (21 days) were also proven for the pentadecanoic acid coating.

Low-surface-energy monomer for ultrathin silicone membrane fabrication: Towards enhanced ethanol/water pervaporation performance

Silicone-based polymers are the most popular materials to prepare pervaporation (PV) membranes for bioethanol recovery from fermentation process. However, the existing silicone composite membranes mostly exhibited limited permeance for ethanol/water separation, which can be attributed to the thick active silicone layers resulting from insufficient spreading of the polymer casting solution on the porous substrate. In the present study, we propose the use of low-surface-energy monomer into casting solution to enhance its spreading ability for ultrathin silicone membrane fabrication. In specific, a poly(dimethyldiethoxylsilane) (PDMDES) casting solution was prepared by limited polymerization of its low-surface-energy monomer dimethyldiethoxylsilane (DMDES), and was then casted on a porous substrate. We show that the surface energy of the partially polymerized casting solution maintained low, and an ultrathin PDMDES active layer with thickness of sub-micrometer size was obtained. The physicochemical properties of the PDMDES membrane were further characterized by ATR-FTIR, XRD and TGA, respectively. Upon optimized preparation and operation conditions, the PDMDES composite membrane exhibited a superior flux of 7565.6 g·m−2·h−1, while maintained a comparable separation factor when compared to traditional PDMS membranes. Our strategy provides new insights into the development of ultrathin silicone membranes for enhanced bioethanol recovery.

Oil-Impregnated Hydrocarbon-Based Polymer Films

Porous surfaces impregnated with a liquid lubricant exhibit minimal contact angle hysteresis with immiscible test liquids, rendering them ideal as self-cleaning materials. Rather than roughening a solid substrate, an increasingly popular choice is to use an absorbent polymer as the “porous” material. However, to date the polymer choices have been limited to expensive silicone-based polymers or complex assemblies of polymer multilayers on functionalized surfaces. In this paper, we show that hydrocarbon-based polymer films such as polyethylene can be stably impregnated with chemically compatible vegetable oils, without requiring any surface treatment. These oil-impregnated hydrocarbon-based films exhibit minimal contact angle hysteresis for a wide variety of test products including water, ketchup, and yogurt. Our oil-impregnated films remain slippery even after several weeks of being submerged in ketchup, illustrating their extreme durability. We expect that the simple and cost-effective nature of our slippery hydrocarbon-based films will make them useful for industrial packaging applications.

Enhanced Adhesion of Polydimethylsiloxane Using an Interlocked Finger Structure.

Silicone-based polymers have been widely used for many applications, but their extremely low surface energies and the resulting poor adhesion have been the cause for continuous problems. Herein, a novel adhesion improvement technique using an interlocked finger structure is demonstrated, which enables up to 24.8 and 7.3-fold increases in adhesion compared to the untreated and conventional plasma-treated cases, respectively. The interlocked finger structure is fabricated by surface-confined dissolution and subsequent directional melt crystallization of a solvent. After removing the solvent crystals, porous surfaces are prepared from polyurethane, polyvinyl alcohol, and polystyrene, and these are used to fabricate interfaces of interlocked finger structures with polydimethylsiloxane. The improvement in adhesion strength linearly depends on the pore depth of the prepared surfaces. This novel technique of surface adhesion could improve the performance of polymers with intrinsically poor adhesion in future applications.

A New Way to Silicone‐Based Peptide Polymers

AbstractWe describe a new class of silicone‐containing peptide polymers obtained by a straightforward polymerization in water using tailored chlorodimethylsilyl peptide blocks as monomeric units. This general strategy is applicable to any type of peptide sequences, yielding linear or branched polymer chains composed of well‐defined peptide sequences.

Crosslinking of Biocatalytically Synthesized Organosilicone Copolymers for Flame Retardant Applications

Crosslinking of polymers using crosslinking agents has been widely utilized to further improve the mechanical and thermal properties of the polymers. We have explored various aliphatic and aromatic dicarboxylic acids such as malonic acid, glutaric acid, isophthalic acid, terephthalic acid and terephthaloyl chloride as crosslinking agents to crosslink polydimethylsiloxane copolymer [poly{poly(dimethylsiloxane-1000)-propylamine-5-aminoisophthaloyl}] to improve its flame retardant properties. We have also used nanoclays [Cloisite 20A, 2C18 MMT (dimethylditallowammonium-/ dimethyldioctadecylammonium-modified montmorillonite)] along with the crosslinker during crosslinking process to further reduce the flammability of the crosslinked polymers. Among all the crosslinkers investigated, isophthalic acid with the nanoclay was found to have the best performance for flame retardant applications. The present work provides a basis to further improve the performance of silicone-based polymers for the flame retardant applications.

Structural and photophysical properties of anthracenyl and carbazolyl groups in silicone-based polymers

This paper describes a simple methodology to attach luminescent groups (anthracenyl and carbazolyl) to polysiloxanes (silicone), using hydrosilylation reactions between the Si–H groups from the silicone precursor to vinyl derivatives of the lumophores. The photophysical properties of these luminescent silicones were studied using both steady-state and dynamical photoluminescence spectroscopy. A strong correlation was obtained between the structural characteristics of the anthracenyl- and carbazolyl-based polysiloxanes, depending on the amount and the position of the Si–H bonds in the silicone precursors. For sparsely distributed Si–H groups, both the anthracenyl-labeled and carbazolyl-labeled polysiloxanes showed photophysical properties (fluorescence spectrum and fluorescence decays) similar to those of 1-alkyl anthracenyl and 1-alkyl carbazolyl derivatives, respectively. Nevertheless, for closely spaced Si–H groups, emission and decay are different. The presence of excimers was observed for anthracenyl but not for carbazolyl polysiloxanes. This latter observation is quite different from that observed for carbon-based polymers for which the carbazolyl excimer formation is a very common process probably due to the differences in the silicone structure.

The effect of density fluctuations in supercritical fluids: new science and technology for polymer thin films

Supercritical carbon dioxide (scCO 2) is being used increasingly as a green solvent in polymer processing. However, the major disadvantage thus far is that only a limited class of polymers, such as fluorinated or silicone-based polymers, can be dissolved in scCO 2. Here we show that large density fluctuations in scCO 2 can significantly enhance the solubility of scCO 2 with polymer thin films even when the bulk polymers have very poor miscibility with scCO 2. In addition, by utilizing quick solvent evaporation of CO 2, we could preserve the swollen structures, resulting in low-density polymer thin films where nanometer-scale porosity was significantly introduced. The use of the low-density polymer thin films could allow us to develop a new gas membrane that could selectively permit a large flow of small molecule gases, such as O 2 and CO 2, while completely blocking out larger gases or particulates.

Preparation and Characteristics of Liquid Silicone Rubber Nanocomposite Containing Ultrafine Magnesium Ferrite Powder

Liquid silicone rubber with high thermal conductivity and effective electromagnetic interference (EMI) shielding properties was prepared. Silicone-based polymers were prepared by the equilibrium polymerization of cyclic siloxane and end-blockers. Magnesium ferrite nanoparticles having spinel magnetic properties were synthesized by the sol-gel method. A liquid silicone rubber (LSR) nanocomposite was prepared by compounding α,ω-vinyl poly(dimethyl/methylpenylsiloxane) prepolymer (VPMPS), α, ω-hydrogen poly(dimethyl/hydrogenmethylsiloxane) prepolymer (HPDHS), catalyst and magnesium ferrite, which was modified with the surface treating agent, 1,3-divinyltetramethyldisilazane (VMS). The microwave absorbing property and thermal conductivity for the LSR nanocomposite-containing magnesium ferrite ultrafine particles, which were modified with the surface treatment agent, exhibited 10∼14 dB of reflection loss at 1∼2 GHz and 1.33 w/mK.

Drug eluting stents [Emerging Technologies

Two main contributing factors to plaque formation and growth. One relates to the triggering role played by inflammatory mediators, such as cytokines. The second relates to the out-of-control growth of smooth-muscle cells. The drug selected to work with a drug-eluting stent should control one or both of these factors. Typically, the drug is entrapped in a polymer coating that slowly releases it into the arterial wall. Polymer materials include bioerodible polymers, such as poly-L lactic acid, and biostable polymers, such as polyurethane derivates and silicone-based polymers.

超臨界流体がつくる高分子超薄膜の新しい構造・物性

Supercritical carbon dioxide (scCO2) is being used increasingly as a green solvent in polymer processing. The major disadvantage thus far is that only a limited class of polymers, such as fluorinated or silicone-based polymers, can be dissolved in CO2. Here I show that large density fluctuations in scCO2 can significantly enhance the solubility of scCO2 in polymer thin films even when the bulk polymers have very poor miscibility with CO2. By using in situ neutron reflectivity, I found that a wide variety of polymer thin films can swell as much as 30-60% when exposed to scCO2 within a narrow temperature and pressure regime, known as the 'density fluctuation ridge', which defines the maximum density fluctuation amplitude in CO2. Furthermore, the swollen structures induced by the density fluctuation could be frozen by a flash evaporation of CO2 via the vitrification process of the polymer without a formation of void structures. X-ray reflectivity clearly showed that the scCO2 process could be used to produce uniform low-density polymer thin films. I also found that other properties of the vitrified films, such as index of refraction, dielectric constant and glass transition, were correlated with the low-density density profile.

Evaluation of silicone-based pressure-sensitive adhesives for transdermal drug delivery [II] effect of penetrant lipophilicitv

AbstractAn adhesive polymer drug dispersion-type transdermal drug delivery (a-TDD) system, consisting of a single drug-loaded adhesive polymer layer sandwitched between a drug-impermeable backing membrane and a detachable release liner, was developed from two silicone-based pressure-sensitive adhesive polymers for the controlled administration of drugs. The effect of variation in penetrant lipophilicity, using a series of testosterone derivatives with an increasing number of methyl groups in the steroid skeleton, on the release kinetics from the a-TDD system and skin permeation rate profiles was investigated. Absence of a methyl group at the 19th position of testosterone increased the flexibility of the steroid molecule and thus yeilded higher diffusivity and greater skin permeation rate. Addition of esters at the 17 s-position resulted in a reduction in diffusivity with an increase in the alkyl chain length of the ester. These esters were found to be bioconverted to testosterone during permeation through...

The Selective Recovery of Alcohols from Fermentation Broths by Pervaporation

Abstract Pervaporation can be successfully utilized to recover various alcohols from fermentation broths and dilute process streams. Hydrophobic membranes, such as silicone-based polymers, have been employed in this application to produce an enriched product. Research in this field has increased dramatically in the past five years and a review of this work is warranted. Fermentations of n-butanol, ethanol, and isopropanol all yielded positive results. The direct integration of a membrane with a bioreactor makes the process more efficient and reduces the effects of product inhibition. A majority of researchers have investigated selective organic permeation from binary aqueous mixtures. These results provide an excellent data base on the permeabilities of alcohols through various membranes. This paper specifically addresses the application of pervaporation to the selective permeation of alcohols from dilute mixtures with particular reference to fermentation broths.

Tunable diode lasers for industrial analysis and monitoring applications

A new generation of infrared instrumentation incorporating tunable diode lasers has been developed for application to industrial analysis and process monitoring problems. Specific advantages of tunability in the mid-infrared, high spectral resolution, and milliwatt range power outputs are discussed and comparisons made to conventional infrared instrumentation. Examples of applications in the areas of on-line process monitoring and quality control of silicone-based polymers, smokestack effluent monitoring, nondestructive quality control testing of quartz-halogen lamps, and quantitative analysis of aqueous based solutions are presented. Conclusions are drawn indicating the potential for further applications in these and related areas.

Tunable Diode Lasers for Industrial Analysis and Monitoring Applications

A new generation of infrared instrumentation incorporating tunable diode lasers has been developed for application to industrial analysis and process monitoring problems. Specific advantages of tunability in the mid-infrared, high spectral resolution, and milliwatt range power outputs are discussed and comparisons made to conventional infrared instrumentation. Examples of applications in the areas of on-line process monitoring and quality control of silicone-based polymers, smokestack effluent monitoring, nondestructive quality control testing of quartz-halogen lamps, and quantitative analysis of aqueous based solutions are presented. Conclusions are drawn indicating the potential for further applications in these and related areas.