Polydimethylsiloxane Oligomers Research Articles

Preparation, Surface Activities, and Biodegradability of a Bola‐Type Collagen Hydrolysate‐Based Siloxane Surfactant

Abstract2 bola‐type collagen hydrolysate‐based siloxane surfactants (CBES) were prepared via grafting of an epoxy‐terminated polydimethylsiloxane oligomer onto 2 collagen hydrolysates with different molecular weights. Their structure was characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy, and the degree of grafting was determined by calculating the free amino content, which confirmed the successful synthesis of CBES. Subsequently, their physicochemical properties, such as particle size and isoelectric point, were evaluated. Besides, surface activities, application functionalities, and biodegradability of CBES were investigated. The results showed that CBES‐1, prepared with the lower‐molecular‐weight collagen hydrolysate, possessed superior surface activity, excellent foaming ability, and good emulsifying capacity comparable to those of a typical emulsifier such as the fatty alcohol polyoxyethylene ether (AEO‐9). In addition, their BOD5/CODCr value and CO2 evolution demonstrated that the CBES are readily biodegradable. There is, therefore, great potential for the bola‐type CBES to be applied in fields such as leather treatment and textile industries.

Janus and Strawberry-like Particles from Azo Molecular Glass and Polydimethylsiloxane Oligomer.

This study investigated Janus and strawberry-like particles composed of azo molecular glass and polydimethylsiloxane (PDMS) oligomer, focusing on controllable fabrication and formation mechanism of these unique structures and morphologies. Two materials, the azo molecular glass (IA-Chol) and PDMS oligomer (H2pdca-PDMS), were prepared for this purpose. The Janus and strawberry-like particles were obtained from the droplets of a dichloromethane (DCM) solution containing both IA-Chol and H2pdca-PDMS, dispersed in water and stabilized by poly(vinyl alcohol). Results show that the structured particles are formed through segregation between the two components induced by gradual evaporation of DCM from the droplets, which is controlled by adding ethylene glycol (EG) into the above dispersion. Without the addition of EG, Janus particles are formed through the full segregation of the two components in the droplets. On the other hand, with the existence of EG in the dispersion, strawberry-like particles instead of Janus particles are formed in the phase separation process. The diffusion of EG molecules from the dispersion medium into the droplets causes the PDMS phase deswelling in the interfacial area due to the poor solvent effect. Caused by the surface coagulation, the coalescence of the isolated IA-Chol domains is jammed in the shell region, which results in the formation of the strawberry-like particles. For the particles separated from the dispersion and dried, the PDMS oligomer phase of the Janus particles can adhere and spread on the substrate to form unique "particle-on-pad" morphology due to its low surface energy and swelling ability, while the strawberry-like particles exist as "standstill" objects on the substrates. Upon irradiation with a linearly polarized laser beam at 488 nm, the azo molecular glass parts in the particles are significantly deformed along the light polarization direction, which show unique and distinct morphologies for these two types of the particles.

A facile and controllable synthesis of dual‐crosslinked elastomers based on linear bifunctional polydimethylsiloxane oligomers

ABSTRACTDual‐crosslinked supramolecular elastomers with the hybrid network consisting of hydrogen bonds and covalent bonds combine the reversibility of hydrogen bond and mechanical properties of covalent crosslinking network. In this article, isocyanate mixture is used as curing agent to prepare dual‐crosslinked elastomer based on bifunctional polydimethylsiloxane under mild condition. This method can effectively build up a hybrid network with the designed structure. A series of elastomers with same hydrogen bond density and variable covalent crosslinking degree are obtained. Swelling measurements and 1H‐NMR spectra confirm the feasibility and controllability of curing method, the increasing of bifunctional isocyanate give rise to higher covalent crosslinking degree, improving the solvent resistance. The studies on viscoelastic property show that the introduction of an irreversible covalent crosslinking network stabilize the hybrid network, restrain the chain movement. The mechanical and self‐healing property studies reveal that the covalent crosslink significantly reinforce the whole network, while the reparable strength seems to mainly depend on the hydrogen bond density. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3760–3768

Model membrane-mediated cell alignment through surface hydrophobicity

ABSTRACTWe show a realization of well-controlled alignments of human lung fibroblast cell parallel to the guided direction achieved by selectively patterned model membranes. The supported lipid bilayer membranes (SLBMs)-mediated cell alignment and selective growth in particular un- derlying surface properties were achieved through peeling-off of the polydimethylsiloxane (PDMS) stamp. We used the PDMS not only as a microfluidic channel to reconstruct model membrane on a hydrophilic surface, but also as a self-inking stamp for the substrate-surface modification by transfer of outmost low-molecular weight PDMS oligomers (S-PDMS). We found that surface hydrophobicity of solid supports is controlled by thermally-assisted stamping methods and this is crucial for the cell adhesion in lipid-free regions.

Anthraquinone Siloxanes as Thickening Agents for Supercritical CO2

A series of aromatic amide-functionalized, low-molecular-weight polydimethylsiloxanes were synthesized, and their solubility and thickening ability in supercritical carbon dioxide (scCO2) were evaluated. Amide-terminated polydimethylsiloxane (PDMS) oligomers with simple or electron-rich aromatic groups were found to be moderate viscosity oils, indicating that the end groups do not interact strongly enough to be thickeners. Attachment of electron-deficient aromatic groups, such as 4-nitrophenyl, biphenyl, or anthraquinone, onto these amides produced solid polysiloxanes, even at relatively higher degrees of polymerization on the PDMS core (x = 40–50). PDMS derivatives with anthraquinone-2-carboxamide (AQCA) end groups were clear, somewhat rubbery solids. These compounds were found to act as thickeners and gelators of hexanes. In addition, they were able to thicken and/or gel mixtures of hexane and scCO2. The best results were obtained with an AQCA-terminated branched PDMS. Branched fluorenone-2-carboxamide ...

Crosslinking mechanism of supramolecular elastomers based on linear bifunctional polydimethylsiloxane oligomers

ABSTRACTSupramolecular elastomers (SESis) were synthesized via a simplified synthesis route on the basis of a linear bifunctional polydimethylsiloxane. Compared with previous synthesis methods, the structure of the product was much clearer. The 1H‐NMR titration results show that the hydrogen‐bond associations in SESis were relatively weak. During 1H‐NMR reaction monitoring, the viscosity analysis of SESis and the model reactions demonstrated a previously neglected covalent crosslinking reaction not only during the reaction process but also during the postprocess; this led to a hybrid network, that is, covalent crosslinking and hydrogen association, in SESis. This finding explained the poor solubility of the SESis, and it provides us with an important way to controllably synthesize this material and adjust its properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43385.

Modulating stability and mechanical properties of silica–gelatin hybrid by incorporating epoxy‐terminated polydimethylsiloxane oligomer

ABSTRACTSilica‐gelatin hybrids, particularly GT‐G hybrids prepared by crosslinking gelatin (G) with γ‐glycidoxypropyltrimethoxysilane (GT), have attracted much attention in tissue engineering for diverse applications in hard or soft tissue regeneration; however, scaffolds with tunable properties are needed to meet specific requirements. In this work, a silica‐gelatin hybrid (ES/GT‐G) was synthesized by incorporating epoxy‐terminated polydimethylsiloxane oligomer (ES) to modulate the properties of GT‐G hybrid. The ES/GT‐G hybrid sponge presented a 3D network structure with porosity 86.4% ± 0.9%, determined by the liquid displacement method, and average pore size 340 ± 36 μm, determined by SEM observation. Compared with GT‐G hybrid material, the prepared ES/GT‐G hybrid wet film showed a decrease of tensile strength from 2.79 ± 0.04 MPa to 1.87 ± 0.12 MPa, with an increase of elongation at break from 19.96 ± 0.66% to 29.86 ± 0.87%, and the ES/GT‐G hybrid sponge exhibited a decline of compressive yield strength from 1.21 ± 0.04 MPa to 0.72 ± 0.06 MPa, based on the tensile and compression tests respectively. The introduction of ES enhanced the thermal denaturing temperature of GT‐G by 5°C as determined by a DSC study, and increased in vitro biodegradation slightly, without significantly changing surface wettability and swelling behavior. These findings suggest that silica‐gelatin hybrids with tunable properties are promising for applications from hard to soft tissue regeneration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43059.

Micropatterned Charge Heterogeneities via Vapor Deposition of Aminosilanes

Aminosilanes are routinely employed for charge reversal or to create coupling layers on oxide surfaces. We present a chemical vapor deposition method to pattern mica surfaces with regions of high-quality aminosilane (3-aminopropyltriethoxysilane, APTES) monolayers. The approach relies on the vapor deposition of an aminosilane through a patterned array of through-holes in a PDMS (poly(dimethylsiloxane)) membrane that acts as a mask. In aqueous solutions the surfaces have regular patterns of charge heterogeneities with minimal topographical variations over large areas. This versatile dry lift-off deposition method alleviates issues with multilayer formation and can be used to create charge patterns on curved surfaces. We identify the necessary steps to achieve high quality monolayers and charge reversal of the underlying mica surface: (1) hexane extraction to remove unreacted PDMS oligomers from the membrane that would otherwise deposit on and contaminate the substrate, (2) oxygen plasma treatment of the top of the membrane surfaces to generate a barrier layer that blocks APTES transport through the PDMS, and (3) low of the vapor pressure of APTES during deposition to minimize APTES condensation at the mica-membrane-vapor contact lines and to prevent multilayer formation. Under these conditions, AFM imaging shows that the monolayers have a height of 0.9 ± 0.2 nm with an increase in height up to 3 nm at the mica-membrane-vapor contact lines. Fluorescence imaging demonstrates pattern fidelity on both flat and curved surfaces, for feature sizes that vary between 6.5 and 40 μm. We verify charge reversal by measuring the double layer forces between a homogeneous (unpatterned) APTES monolayers and a mica surface in aqueous solution, and we characterize the surface potential of APTES monolayers by measuring the double-layer forces between identical APTES surfaces. We obtain a surface potential of +110 ± 6 mV at pH 4.0.

Magnetic, Fluorescent, and Copolymeric Silicone Microspheres.

Silicone microspheres are exceedingly difficult to make. Here, polydimethylsiloxane microspheres (≈1 μm diameter) are synthesized using ultrasonic spray pyrolysis, the first demonstration of a scalable synthetic procedure for crosslinked silicone microspheres. This continuous, aerosol process is also used to directly produce fluorescent, magnetic, and copolymeric derivatives; the potential biomedical applications of these microspheres are explored.

Flexible Distributed Bragg Reflectors from Nanocolumnar Templates.

A flexible distributed Bragg reflector is made by the infiltration of a nanocolumnar array with polydimethyl siloxane oligomers. The high optical reflectance displayed by the final material is a direct consequence of the high refractive index contrast of the columnar layers whereas the structural stability is due to the polymer properties.

Novel supramolecular elastomer films based on linear carboxyl-terminated polydimethylsiloxane oligomers: preparation, characterization, biocompatibility, and application in wound dressings

A novel supramolecular elastomer (SESi) based on multiple hydrogen bond associations between low-molecular-weight polydimethylsiloxane chains was obtained through a two-step reaction of linear carboxyl-terminated polydimethylsiloxane oligomers with diethylenetriamine and urea, and the reaction mechanism was characterized. The results of differential scanning calorimetry and X-ray diffraction analyses indicated that the supramolecular network structure is completely amorphous, endowing SESi with rubber-like elastic behavior at room temperature. The transparent SESi film prepared by hot pressing displayed nice viscoelasticity, benign water absorption, water vapor transition rates, and ideal biocompatibility; and did not show cytotoxicity or skin irritation. These properties allow the elastomer to function as an occlusive wound dressing. To demonstrate its potential in wound dressings, a detailed comparison of commercial 3M Tegaderm™ film and the SESi film was conducted. The SESi film exhibited similar effects in wound healing, and the wound bed was covered by the SESi film without the occurrence of significant adverse reactions.

The synthesis and characterization of supramolecular elastomers based on linear carboxyl-terminated polydimethylsiloxane oligomers

Supramolecular elastomers obtained through a two-step reaction of linear carboxyl-terminated polydimethylsiloxane oligomers (PDMS–COOH2) with diethylenetriamine (DETA) and urea show reasonable hysteresis and acceptable self-healing properties.

Synthesis, characterization and morphological studies of some novel siloxane-based block copolymeric materials containing organometallic as well as organic polyesteramides

A series of semi-aromatic diamine monomers (1,m-bis (4-amino benzoyloxy) alkanes; m = 2–6) having in-built ester linkages with variable methylene spacers were synthesized in two steps from aliphatic diols and p-nitrobenzoyl chloride and characterized by their melting points, elemental analysis, FTIR, 1H and 13C NMR spectroscopic studies. The diamines were then polymerized in-situ with ferrocene-based organometallic and terephthaloyl- as well as isophthaloyl-based organic acyl chlorides along with telechelic polydimethylsiloxane oligomer to produce a novel set of ferrocene-containing siloxane-based block copolymers and their organic analogues. The corresponding polyesteramides of the synthesized copolymers, without siloxane segment, were also prepared for comparative studies. The structural features of the organometallic and organic block copolymers along with their respective polyesteramides were confirmed by their physical properties and spectroscopic studies. The molecular parameters of all these materials were determined by static laser light scattering (LLS) technique and glass transition temperatures (Tg) were obtained by differential scanning calorimetry (DSC). The materials were soluble in sulphuric acid and partially soluble in common organic solvents at room temperature, yet become readily soluble upon N-trifluoroacetylation. The morphological information of the synthesized materials was obtained by X-ray diffraction and surface studies (SEM and AFM).

The nucleation study on the cationic miniemulsion polymerization of octamethylcyclotetrasiloxane (D4)

The nucleation of the cationic miniemulsion polymerization of octamethylcyclotetrasiloxane (D4) has been investigated in detail in this work. The particle size was traced by dynamic laser scattering in the polymerization process using different concentration of dodecylbenzenesulfonic acid (DBSA) as both the initiator and surfactant. The results reveal the progressively decreasing particle sizes with the steadily increasing monomer conversion. The descending particle sizes can be explained by the existence of homogeneous nucleation of hydroxyl-terminated polydimethylsiloxane (PDMS) oligomers in addition to the primary droplet nucleation. A linear relationship between the natural logarithm of the average particle diameter (lnd(t)) and the natural logarithm of the monomer conversion (lnf(t)) is then deduced based on the theory, which has been validated by the experimental data. The slope of lnd(t)~lnf(t) line relies on the parameter of K which is the ratio of PDMS oligomers entering water phase to all PDMS oligomers produced. The influence of DBSA concentration on the K and the fraction of homogeneous nucleation (F(H)) has been then obtained. Both of the values of K and F(H) increase with the increasing DBSA concentrations.

Evaluation of polydimethylsiloxane (PDMS) surface modification approaches for microfluidic applications

Motivated by stabilizing a hydrophilic surface condition of polydimethylsiloxane (PDMS) and improving its zeta potential, several reported methods for treating PDMS surface were evaluated using two or more of the following techniques: capillary flow in dryly stored channels, static contact angle measurement, current monitoring technique and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The surface treatment methods that were evaluated include four groups: pre-doping PDMS with acrylic acid, extraction of uncured PDMS (oligomer), and monomer grafting using 2-hydroxyethyl methacrylate (HEMA) and monomer grafting using polyethylene glycol (PEG). This study also proposed a modified PEG grafting method. It was observed that the extraction and monomer grafting methods were capable of changing hydrophobic PDMS to the stable hydrophilic state. However, none of the evaluated methods were able to increase the zeta potential of PDMS to a value higher than that treated with a one-step plasma treatment based on the current monitoring measurement, where 1X Tris–Borate–EDTA (TBE) buffer was used as the liquid sample. It was found that combining extraction and one-step plasma treatment was the best approach to maintain the stable hydrophilic state of PDMS and gain a relatively high zeta potential. In addition, it was found that the extraction method provided the most consistent outcome in modified PDMS surfaces compared to other methods.

Hydrophilic simultaneous interpenetrating polymer network silicone hydrogels prepared by hybrid photopolymerization

Hydrophilic silicone hydrogels have been prepared by UV-initiated free radical/cationic hybrid polymerization of acrylate oligomer polyethylene glycol diacrylate (PEGDA) and bifunctional vinyl ether terminated polydimethylsiloxane oligomer (VESi). PEGDA was shown to polymerize faster and more extensively than VESi, which was further consumed upon storage of the sample in the dark. The radical polymerization of PEGDA was affected by the oxygen inhibition effect, while the cationic polymerization of VESi was influenced by the atmosphere humidity. The presence of a nucleophile acetic acid could hinder the polymerization of VESi, but exerted less influence on the polymerization of PEGDA. The results of the contact angle measurements indicated that highly hydrophilic surfaces were obtained by the interpenetrating polymer network technique.

Study on the preparation and properties of novel block copolymeric materials based on structurally modified organometallic as well as organic polyamides and polydimethylsiloxane

AbstractSome novel ferrocene‐containing polyamide‐based block copolymer materials with telechelic polydimethylsiloxane oligomer and their organic analogues were prepared by solution‐phase polycondensation of ferrocene‐based organometallic and terephthaloyl‐ as well as isophthaloyl‐based organic acyl chlorides with a series of semi‐aromatic diamines having ether linkages together with variable aliphatic character. The corresponding polyamides of the synthesized materials, without polydimethylsiloxane segment, were also prepared for comparison of physicochemical properties. None of the synthesized organometallic and organic block copolymers along with their respective polyamides melted below 300 °C and their structural features were confirmed by their physical properties and spectroscopic studies. The weight‐average molecular weights and molecular parameters of all these materials were determined by the static laser light scattering technique. The materials were soluble in sulfuric acid and partially soluble in common organic solvents, and yet became readily soluble upon N‐trifluoroacetylation. The synthesized materials were further characterized by their water absorption characteristics, X‐ray diffraction studies and surface morphology (SEM and AFM) and thermal (DSC and TG) analyses, and their structure–property relationships were elucidated from these studies. The energies of pyrolysis for these materials were calculated by the Horowitz and Metzger method. © 2012 Society of Chemical Industry

Surface modification of PDMS by atmospheric-pressure plasma-enhanced chemical vapor deposition and analysis of long-lasting surface hydrophilicity

Atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) offers several benefits such as simplicity, high productivity, and versatility. An AP-PECVD-based method is proposed in this study to modify hydrophobic PDMS (polydimethylsiloxane) surfaces towards a long-lasting hydrophilic character. To enhance the sustainability of the hydrophilicity, two kinds of layers were sequentially deposited by AP-PECVD on the surface of a PDMS block (TEOS-O2/CH4/PDMS). A hydrocarbon layer was first coated on the bare PDMS surface using CH4 as the reactant, and then, a hydrophilic SiOx layer was deposited using tetraethyl orthosilicate and oxygen (TEOS-O2). The highly cross-linked hydrocarbon layer acted as a physical barrier layer (PBL) between the bare PDMS surface and the hydrophilic layer. To confirm that the PBL suppresses the hydrophobic recovery of the modified PDMS surface with double layer, a single-layer-coated PDMS sample (TEOS-O2/PDMS) without the PBL was prepared by AP-PECVD using TEOS-O2. The surface characteristics were determined by static contact angle measurements, surface roughness measurements, and surface chemical composition/chemical bonding determination and compared with those of modified PDMS surface with double layer. The surface morphology of TEOS-O2/PDMS degraded seriously by the diffusion of PDMS oligomers to the hydrophilic layer, but that of TEOS-O2/CH4/PDMS was sustained for a long time. Thus, TEOS-O2/CH4/PDMS had the lowest contact angle, almost 0°, and showed long-lasting surface hydrophilicity, with almost no change in the contact angle for 28 days. Thus, this proposed method is confirmed to be well suited for use in applications that require stable hydrophilic surface property in PDMS.

Universal Nanopatternable Interfacial Bonding

A nanopatternable polydimethylsiloxane (PDMS) oligomer layer is demonstrated as an interfacial adhesive for its intrinsic transferability and universal adhesiveness. Utilizing the well-established surface modification and bonding techniques of PDMS surfaces, irreversible bonding is formed (up to 400 kPa) between a wide range of substrate pairs, representing ones within and across different materials categories, including metals, ceramics, thermoset, and thermoplastic polymers.

Multiscale Modeling of the Morphology and Properties of Segmented Silicone-Urea Copolymers

Molecular dynamics and mesoscale dynamics simulation techniques were used to investigate the effect of hydrogen bonding on the microphase separation, morphology and various physicochemical properties of segmented silicone-urea copolymers. Model silicone-urea copolymers investigated were based on the stoichiometric combinations of α,ω-aminopropyl terminated polydimethylsiloxane (PDMS) oligomers with number average molecular weights ranging from 700 to 15,000 g/mole and bis(4-isocyanatocyclohexyl)methane (HMDI). Urea hard segment contents of the copolymers, which were determined by the PDMS molecular weight, were in 1.7–34% by weight range. Since no chain extenders were used, urea hard segments in all copolymers were of uniform length. Simulation results clearly demonstrated the presence of very good microphase separation in all silicone-urea copolymers, even for the copolymer with 1.7% by weight hard segment content. Experimentally reported enhanced properties of these materials were shown to stem from strong hydrogen bond interactions which leads to the aggregation of urea hard segments and reinforcement of the PDMS.