PDMS Oligomers Research Articles

Polymers Containing Diethylsiloxane Segment and Active Functional Group by Ring-Opening Polymerization of Hexaethylcyclotrisiloxane under the Catalysis of Linear Chlorinated Phosphazene Acid.

Linear chlorinated phosphazene acid is prepared using PCl5 and NH4Cl as raw materials. Using hexaethylcyclotrisiloxane as the monomer, 1,1,3,3-tetramethyldisiloxane or 1,3-divinyl-1,1,3,3-tetramethyldisiloxane as the end-capping agent, and linear chlorinated phosphazene acid as the catalyst, polydiethylsiloxane oligomers terminated with active Si-H or Si-CH=CH2 groups have been prepared. Using hexaethylcyclotrisiloxane and 1,3,5,7-octamethylcyclotetrasiloxane as comonomers, 1,1,3,3-tetramethyldisiloxane or hexamethyldisiloxane as the end-capping agent, or using hexaethylcyclotrisiloxane and octamethylcyclotetrasiloxane as comonomers, 1,1,3,3-tetramethyldisiloxane as the end-capping agent, copolymers containing active Si-H bonds and dimethylsiloxane segments have been prepared under the catalysis of linear chlorinated phosphazene acid. The effects of catalyst dosage, reaction temperature, reaction time, end-capping agent, and polymerization monomer dosage on polymer yield and structure were investigated. Using 300 ppm of linear chlorinated phosphazene acid, oligomers and copolymers containing an active Si-H bond and diethylsiloxane segment were prepared under mild conditions. The molecular weight of the obtained polymers was close to their designed values, but their PDI values were small. The highest yield of α, ω-bisdimethylsiloxyl-terminated PDES oligomers reached 93%. Using oligomers and copolymers containing Si-H bonds and diethylsiloxane segments as crosslinkers, a silicone gel containing diethylsiloxane segments was prepared by hydrosilylation reaction. With the introduction of a diethylsiloxane segment, the glass transition temperature of the silicone gel decreased relative to that of the PDMS oligomer, but the temperature at 5% weight loss in nitrogen atmosphere decreased from 347 °C to 312 °C. The mechanism of the ring-opening polymerization of hexaethylcyclotrisiloxane catalyzed by linear chlorinated phosphazene acid is also discussed.

Construction of the Stable Lubricant Film on One-Dimensional Cone-Structured Surfaces for Directional Liquid Transport.

Directional liquid transport along one-dimensional structures finds vast applications in fog harvest, liquid separation, sensing, chemical synthesis, and numerous other scenarios. Dynamically, the liquid transport speed is boosted by the driving force and retarded by the hysteresis from the liquid/substrate interface. A capillary force-relied lubricant film or a covalently attached polymer brush on the surface could increase liquid mobility temporarily by reducing the interfacial hysteresis. However, the easy depletion of the lubricant film and the stringent restriction of the substrate severely hamper droplet's directional transport in a long run. Herein, we report a feasible and durable hysteresis reduction design with the polymer-brush stabilized lubricating surface (PBSLS). The PBSLS is achieved through incorporating liquid-like polydimethylsiloxane brushes (b-PDMS) and the liquid PDMS oligomer (o-PDMS). The covalent attached b-PDMS "locks" the lubricant oil o-PDMS to the cone surface via strong intermolecular van der Waals force in between. The PBSLS on the cone surface can be sustained under constant shearing force from liquid transport for at least 6 h. A cone with such PBSLS shows increased ability of droplet transport and enhanced fog collection performance in the long run. This design supplies an effective way toward regulating macro-level interfacial performance through surface design on the molecular level.

Derivation of the toxicological threshold of silicon element in the extractables and leachables from the pharmaceutical packaging and process components.

Silicon is one of the most monitored elements in extractables and leachables studies of pharmaceutical packaging systems and related components. There is a need to review and evaluate toxicological thresholds of silicon because of its direct contact with drug products (DP) especially a liquid form of DP with the widely used pharmaceutical packaging systems made of silicon materials like glass and silicone. It is required by regulatory authorities to test silicon content in DP; however, there are no official guidelines on the toxicology of silicon that are currently available, yet the knowledge of toxicological thresholds of silicon is critical to justify the analytical limit of quantification (LOQ). Therefore, we reviewed the toxicity of silicon to derive a toxicological threshold by literature review of toxicity studies of both inorganic and organic silicon compounds. Oral toxicity is low for inorganic silicon like silicon dioxide or organic silicon polymers such as silicone tube/silicone oil (polydimethylsiloxane, or namely, PDMS as the major ingredient). In comparison, inhalational toxicity of silicon dioxide leads to pulmonary silicosis or even lung cancer. When orally administered, the toxicity of silicon dioxide, glass, polymers, or PDMS oligomers varies depending on their morphology, molecular weight (MW), and degrees of polymerization. PDMS with high MW has minimal toxic symptoms with non-detectable degradation/elimination by both intraperitoneal and subcutaneous administration routes, while exposure to either PDMS or small molecule dimethyl silicone compounds by the intravenous administration route may lead to death. We here determined a general parenteral permitted daily exposure (PDE) of 93μg/day for inorganic silicon element and 100μg/day for organic silicon element by reviewing toxicological data of both forms of silicon. In conclusion, this work provides evidence for pharmaceutical companies and regulatory agencies on the PDEs of silicon elements in pharmaceutical packaging and process components through a variety of administration routes.

Alkylsiloxane/alkoxysilane sols as hydrophobic treatments for concrete: A comparative study of bulk vs surface application

Water and waterborne decay agents (e.g. salts, microorganisms) are commonly associated with undesired alterations and damages on concrete elements. A strategy to mitigate their impact is to decrease water retention in the material either by surface treatments or admixtures. In this work, hydrophobic concretes were developed by the addition of a hydrophobic sol containing TEOS and PDMS oligomers, synthetized by a surfactant-assisted sol-gel route, either as an admixture or as a surface treatment. The hydrophobic performance was similar for both application modes (>70% capillary absorption reduction) and higher than concrete containing a commercial (calcium stearate) admixture or a nanosilica-based hydrophobic coating. Addition as an admixture led to a higher durability in the rain and abrasion tests.The hydrophobic sol as an admixture promotes an increase of surface roughness and porosity, as well as the formation of C–S–H like reaction products with the cement matrix components, as evidenced by AFM, MIP, SEM and FTIR. Despite the higher porosity, impact resistance and material cohesion were not negatively affected respect to the plain concrete. Application as a surface treatment decreased porosity and led to a higher amorphous SiO2 content. The material cohesion and impact resistance was increased by this application, although penetration was limited to the first 4 mm and the hydrophobic properties were more susceptible to mechanical damages to the surface.

Viscoelastic properties and self‐healing behavior in a family of supramolecular ionic blends from silicone functional oligomers

Supramolecular solid‐like polymer gels were obtained, through acid‐base interactions, starting from highly viscous amino‐terminated and carboxylic‐terminated telechelic PDMS oligomers, with different molecular weights, ranging approximately from 900 to 27 000 g/mol. The obtained blends were studied and characterized in terms of viscoelastic behavior, tensile properties, and self‐healing abilities, with the aim of gaining a better understanding of structure‐property relationships in these supramolecular ionic blends. IR spectroscopy confirmed the formation of supramolecular ionic interactions thanks to the presence of ammonium carboxylate group absorbance. Thermal analysis showed the formation of a crystalline phase at room temperature in some of the supramolecular blends when the molecular weight was lower than 27 000 g/mol. An increase in crystallinity by decreasing the chain length and therefore their molecular weights was also observed. These supramolecular PDMS materials showed self‐healing abilities with a value of healing efficiency ranging from 25% up to 52%. Samples tested with creep recovery analyses showed a viscoelastic behavior. Interpolation of the creep curves according to the four‐parameter Voigt model provides a relationship between the viscoelastic behavior of these PDMS materials and their self‐healing abilities. Our results show how the control of the thermal, viscoelastic, and mechanical properties of these materials allows the design of supramolecular blends based on acid‐base interactions with improved self‐healing properties.

Poly(dimethylsiloxane) Stamp Coated with a Low-Surface-Energy, Diffusion-Blocking, Covalently Bonded Perfluoropolyether Layer and Its Application to the Fabrication of Organic Electronic Devices by Layer Transfer.

It is demonstrated that a stamp composed of a poly(dimethylsiloxane) (PDMS) bulk and perfluoropolyether (PFPE) coating fabricated by a simple dip-coating method has the following properties that are ideal for the transfer patterning of various materials. Deposited by a condensation reaction between PDMS and PFPE molecules as well as the adjacent PFPE molecules, the PFPE coating has a strong adhesion to the PDMS surface and strong internal cohesion, while providing a low energy surface. Furthermore, it is found to function as a bidirectional diffusion barrier: it effectively prevents organic small molecules deposited on the stamp from being absorbed into free volumes of PDMS; it also prevents PDMS oligomers from migrating onto the layer to be transferred, thereby avoiding the contamination of that layer. Morphological and elemental characterization of the surfaces of the transferred organic semiconductor and graphene layers confirms a successful transfer with a high degree of surface cleanliness. The quality of interfaces mechanically bonded using the PFPE-coated stamps and the cleanliness of the transferred layers are remarkably high that the electronic functions of a transfer-bonded organic heterojunction are comparable to those of the same interface formed by vacuum deposition, and that the charge transport across the transfer-bonded graphene-graphene and graphene-MoO3 interfaces is efficient. Our results demonstrate that the PFPE-coated stamp enables patterned depositions of materials with high quality interfaces while avoiding a high temperature or wet process.

Adaption of a parallel-path poly(tetrafluoroethylene) nebulizer to an evaporative light scattering detector: Optimization and application to studies of poly(dimethylsiloxane) oligomers as a model polymer

The adaption of an parallel-path poly(tetrafluoroethylene)(PTFE) ICP-nebulizer to an evaporative light scattering detector (ELSD) was realized. This was done by substituting the originally installed concentric glass nebulizer of the ELSD. The performance of both nebulizers was compared regarding nebulizer temperature, evaporator temperature, flow rate of nebulizing gas and flow rate of mobile phase of different solvents using caffeine and poly(dimethylsiloxane) (PDMS) as analytes. Both nebulizers showed similar performances but for the parallel-path PTFE nebulizer the performance was considerably better at low LC flow rates and the nebulizer lifetime was substantially increased. In general, for both nebulizers the highest sensitivity was obtained by applying the lowest possible evaporator temperature in combination with the highest possible nebulizer temperature at preferably low gas flow rates. Besides the optimization of detector parameters, response factors for various PDMS oligomers were determined and the dependency of the detector signal on molar mass of the analytes was studied. The significant improvement regarding long-term stability made the modified ELSD much more robust and saved time and money by reducing the maintenance efforts. Thus, especially in polymer HPLC, associated with a complex matrix situation, the PTFE-based parallel-path nebulizer exhibits attractive characteristics for analytical studies of polymers.

Development and characterization of a stable adhesive bond between a poly(dimethylsiloxane) catheter material and a bacterial biofilm resistant acrylate polymer coating.

Catheter associated urinary tract infections are the most common health related infections worldwide, contributing significantly to patient morbidity and mortality and increased health care costs. To reduce the incidence of these infections, new materials that resist bacterial biofilm formation are needed. A composite catheter material, consisting of bulk poly(dimethylsiloxane) (PDMS) coated with a novel bacterial biofilm resistant polyacrylate [ethylene glycol dicyclopentenyl ether acrylate (EGDPEA)-co-di(ethyleneglycol) methyl ether methacrylate (DEGMA)], has been proposed. The coated material shows excellent bacterial resistance when compared to commercial catheter materials, but delamination of the EGDPEA-co-DEGMA coatings under mechanical stress presents a challenge. In this work, the use of oxygen plasma treatment to improve the wettability and reactivity of the PDMS catheter material and improve adhesion with the EGDPEA-co-DEGMA coating has been investigated. Argon cluster three dimensional-imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to probe the buried adhesive interface between the EGDPEA-co-DEGMA coating and the treated PDMS. ToF-SIMS analysis was performed in both dry and frozen-hydrated states, and the results were compared to mechanical tests. From the ToF-SIMS data, the authors have been able to observe the presence of PDMS, silicates, salt particles, cracks, and water at the adhesive interface. In the dry catheters, low molecular weight PDMS oligomers at the interface were associated with poor adhesion. When hydrated, the hydrophilic silicates attracted water to the interface and led to easy delamination of the coating. The best adhesion results, under hydrated conditions, were obtained using a combination of 5 min O2 plasma treatment and silane primers. Cryo-ToF-SIMS analysis of the hydrated catheter material showed that the bond between the primed PDMS catheter and the EGDPEA-co-DEGMA coating was stable in the presence of water. The resulting catheter material resisted Escherichia coli and Proteus mirabilis biofilm colonization by up to 95% compared with uncoated PDMS after 10 days of continuous bacterial exposure and had the mechanical properties necessary for use as a urinary catheter.

A facile cost-effective method for preparing robust self-cleaning transparent superhydrophobic coating

This paper reports an easy method to prepare transparent superhydrophobic coating by two-step spray-coating method. In order to improve robustness, PDMS oligomers were used to bond the SiO2 nanoparticle/fluoroalkylsilane composite coating to the substrate. The transmittance of coated glass was above 80 % for wavelengths larger than 500 nm. Moreover, the prepared coating exhibited excellent self-cleaning properties in either air or oil environment. Furthermore, this coating retained superhydrophobic properties after three cycles of abrasion test or strong acid/base attack. Therefore, this robust self-cleaning transparent superhydrophobic coating may have a wide range of practical applications in the optical industry.

Impact of Hydrogen Bonding on Dynamics of Hydroxyl-Terminated Polydimethylsiloxane

Dielectric spectroscopy, rheology, and differential scanning calorimetry were employed to study the effect of chain-end hydrogen bonding on the dynamics of hydroxyl-terminated polydimethylsiloxane. We demonstrate that hydrogen bonding has a strong influence on both segmental and slower dynamics in the systems with low molecular weights. In particular, the decrease in the chain length leads to an increase of the glass transition temperature, viscosity, and fragility index, at variance with the usual behavior of nonassociating polymers. The supramolecular association of hydroxyl-terminated chains leads to the emergence in dielectric and mechanical relaxation spectra of the so-called Debye process traditionally observed in monohydroxy alcohols. Our analysis suggests that the hydroxyl-terminated PDMS oligomers may associate in brush-like or chain-like structures, depending on the size of their covalent chains. The effective length of the linear-associated chains was estimated from the rheological measurements.

Synthesis and structure-property behavior of polycaprolactone-polydimethylsiloxane-polycaprolactone triblock copolymers

Poly(ε-caprolactone)–polydimethylsiloxane–poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymers with a wide range of block lengths (1000–32,000 g/mol) were synthesized by the ring-opening polymerization of ε-caprolactone using aminopropyl terminated PDMS oligomers as the initiator. Reactions were carried out in bulk or solution at 125 ± 5 °C under the catalytic action of tin octoate. Products obtained in high yields were characterized by FTIR spectroscopy, gel permeation chromatography, X-ray diffraction, temperature-dependent optical microscopy, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and static water contact angle measurements. Effect of the polymer composition and the molecular weight of the PDMS and PCL blocks on; (i) copolymer morphology and the extent of microphase separation, (ii) crystallization of PCL segments and (iii) surface properties of copolymers were investigated. Regardless of the block lengths, all PCL-PDMS-PCL copolymers displayed well microphase separated morphologies. The extent of microphase separation, resultant morphology and sizes of the microphases were strongly dependent on the copolymer composition and the block lengths of both PCL and PDMS segments. Crystalline PCL microphase was observed in all copolymers, which increased as a function of PCL content and molecular weight. Hydrophobicity of the copolymer surfaces was improved with increasing PDMS molecular weight, as determined by static water contact angle measurements.

Negative printing by soft lithography.

In inkless microcontact printing (IμCP) by soft lithography, the poly(dimethylsiloxane) (PDMS) stamp transfers uncured polymer to a substrate corresponding to its pattern. The spontaneous diffusion of PDMS oligomers to the surface of the stamp that gives rise to this deleterious side effect has been leveraged to fabricate a variety of devices, such as organic thin film transistors, single-electron devices, and biomolecular chips. Here we report an anomalous observation on a partially cured PDMS stamp where the transfer of oligomers onto Au occurred on regions that were not in contact with the stamp, while the surface in contact with the stamp was pristine with no polymer. On the SiO2 surface of the same chip, as expected, the transfer of PDMS occurred exclusively on regions in contact with the stamp. The printing on Au was quantified by a novel method where the submonolayer of PDMS transfer was measured by probing the local electrochemical passivation of the Au. The local transfer of polymer on SiO2 (and also Au) was measured by selective deposition of Au nanoparticle necklaces that exclusively deposited on PDMS at submonolayer sensitivity. It was discovered that the selectivity and sharpness of PDMS deposition on Au for inkless printing (i.e., negative) is significantly better than the traditional (positive) microcontact printing where the stamp is "inked" with low molecular weight PDMS.

Poly(dimethylsiloxane)-supported ionogels with a high ionic liquid loading.

The immiscibility of poly(dimethylsiloxane) (PDMS) and ionic liquids (ILs) was overcome to create PDMS-supported IL gels (ionogels) with IL loadings of up to 80% by mass through a simple sol-gel reaction at room temperature. By stirring a mixture of a functionalized PDMS oligomer, formic acid, and an IL (or lithium-in-IL solution), a resin was formed that could be cast to create a freestanding, flexible ionogel. PDMS-supported ionogels exhibited favorable ionic conductivity (ca. 3 mS cm(-1)) and excellent mechanical behavior (elastic modulus: ca. 60 kPa; fatigue life: >5000 cycles; mechanically stable at temperatures up to 200 °C). The activation energy of ionic conductivity was shown to be nearly identical for the ionogel and the neat IL, in contrast to ionogel systems wherein the scaffold material is miscible with the IL. This similarity indicates that IL/scaffold chemical interactions are key to the understanding of ionogel electrical performance, especially at elevated temperatures.

Poly(dimethylsiloxane)‐Supported Ionogels with a High Ionic Liquid Loading

AbstractThe immiscibility of poly(dimethylsiloxane) (PDMS) and ionic liquids (ILs) was overcome to create PDMS‐supported IL gels (ionogels) with IL loadings of up to 80 % by mass through a simple sol–gel reaction at room temperature. By stirring a mixture of a functionalized PDMS oligomer, formic acid, and an IL (or lithium‐in‐IL solution), a resin was formed that could be cast to create a freestanding, flexible ionogel. PDMS‐supported ionogels exhibited favorable ionic conductivity (ca. 3 mS cm−1) and excellent mechanical behavior (elastic modulus: ca. 60 kPa; fatigue life: >5000 cycles; mechanically stable at temperatures up to 200 °C). The activation energy of ionic conductivity was shown to be nearly identical for the ionogel and the neat IL, in contrast to ionogel systems wherein the scaffold material is miscible with the IL. This similarity indicates that IL/scaffold chemical interactions are key to the understanding of ionogel electrical performance, especially at elevated temperatures.

Perfluorinated poly(dimethylsiloxane) via the covalent attachment of perfluoroalkylsilanes on the oxidized surface: Effects on zeta-potential values

Poly(dimethylsiloxane) (PDMS) is a widely-used polymer in microfluidic devices due to its range of physical and chemical properties suitable for molding micron-sized features. However, its hydrophobicity also leads to some limitations: it poorly supports electro-osmotic flow, and can be incompatible with biomolecules and with many organic solvents. Surface modification is commonly used to vary PDMS surface properties to make it more suitable for specific microfluidic applications. Here, we report on the surface modification of PDMS using perfluoroalkane–triethoxysilanes, via the covalent attachment of triethoxysilane groups on plasma-oxidized PDMS. A device constructed from such fluorinated materials could be used for separating fluorous-tagged proteins or peptides. Modified PDMS were characterized using a range of surface analytical methods. In particular, zeta- (ζ-) potential values at the interfaces of both modified and unmodified PDMS and under varying pH conditions were measured, as ζ-potential is an essential parameter to support electroosmotic flow (EOF), a common pumping method in microfluidic devices. The results showed the length of fluorinated alkane chain has significant effect on the density of surface modifying species and topography following modification. In addition, the perfluorinated modification increases the magnitude of the ζ-potential at the PDMS interface when compared to that of native PDMS, increasing the electro-osmotic flow rate, over a wide pH range. The modified surface is resistant to the diffusion of PDMS oligomers that affects other PDMS surface modification processes.

Universal Anisotropically Conductive Nano-adhesive of PDMS Oligomers

ABSTRACTA nanopatternable oligomeric PDMS layer has been first verified as a nano-adhesive for its intrinsic transferability and universal adhesiveness. Utilizing the well-established PDMS surface modification and bonding techniques, we have been able to form irreversible bonding between a wide range of substrate pairs, representing ones within and across different material categories, including metals, ceramics, thermoset, and thermoplastic polymers. The anisotropic conductivity of the PDMS oligomer nano-adhesive has been investigated, which allows specific and excellent directional conductivity between bonded electrodes without risk of electrical shorts across different contacts.

Polymer in situ embedding for highly flexible, stretchable and water stable PEDOT:PSS composite conductors

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and polydimethylsiloxane (PEDOT:PSS@PDMS) composite conductors have been obtained by embedding PDMS oligomers and curing agents into a 3D PEDOT:PSS aerogel. The novel 3D elastic network formed by in situ polymerization serves as a support for this brittle aerogel. The as-prepared PEDOT:PSS@PDMS conductors show highly flexible, stretchable and water stable properties.

Efficient desulfurization by polymer–inorganic nanocomposite membranes fabricated in reverse microemulsion

The sulfur in gasoline will convert to SO2 after combustion under high temperature, which adversely affects human health and the environment. Membrane technique in particular pervaporation offers a number of potential advantages over conventional FCC gasoline desulfurization processes. The present study focuses on the performance enhancement of PDMS membrane by incorporating silica nanoparticles. Specifically, silica nanoparticles formed by the catalysis and templating of protamine in w/o reverse microemulsion are in situ embedded into PDMS bulk matrix, endowing the resultant oleophilic nanocomposite membranes with appropriate free volume properties and superior separation performance. Through the rational manipulation of biomimetic mineralization at water–oil interface, silica particles with uniform size are acquired. Following this protocol, by introducing organic PDMS oligomers into the oil phase, PDMS–SiO2 nanocomposite membranes are prepared in a facile way. The resultant nanocomposite membranes display superior permeability and permselectivity in the pervaporative desulfurization using thiophene/n-octane binary mixture as model gasoline, for example, under the condition of 500ppm sulfur in feed (40L/h) at 30°C, an enrichment factor of 4.83–5.82 with a normalized permeation rate of 6.61–10.76×10−5kgm/m2h is acquired.

Fumed silica filled poly(dimethylsiloxane-urea) segmented copolymers: Preparation and properties

Novel fumed silica filled thermoplastic poly(dimethylsiloxane-urea) (TPSU) segmented copolymers were synthesized and characterized. TPSU copolymers were prepared from a cycloaliphatic diisocyanate, aminopropyl terminated PDMS oligomers with number average molecular weights of 3,200, 10,800 and 31,500 g/mol and 2-methyl-1,5-diaminopentane chain extender. Two different types of fumed silica HDK H2000 (hydrophobic) and HDK N20 (hydrophilic) were utilized and incorporated into silicone-urea copolymers in amounts of 1–60% by weight. Influence of the silica type (hydrophilic versus hydrophobic), amount of silica loading and the PDMS soft segment molecular weight on the morphology, tensile properties and modulus-temperature behavior of the nanocomposites were determined. Major observations of this study were: (i) under the blending conditions used, incorporation of silica does not seem to interfere significantly with the hydrogen bonding between urea groups, (ii) incorporation of silica does not affect the glass transition temperature of PDMS, (iii) incorporation of silica influences the tensile and thermomechanical properties of silicone-urea segmented copolymers significantly, (iv) average molecular weight of the PDMS soft segment in the silicone-urea copolymer plays a critical role on the improvement of the tensile properties of the fumed silica/TPSU composites.

Controlling Molecular Mobility in Polymer Matrices: Synchronizing Switching Speeds of Multiple Photochromic Dyes

We report a method that allows the facile synchronization of multiple photochromic dyes in a rigid polymer lens matrix together with large increases in their switching speeds. This was achieved by simple chromatographic fractionation of dye−poly(dimethylsiloxane) (PDMS) conjugates to provide tunable switching speeds with longer PDMS tails providing faster switching speeds and shorter tails providing slower switching with no effect on the electronic nature of the dyes. This was done for mono end-functional dye−PDMS conjugates (one dye at one end of the PDMS) and new telechelic dye−PDMS conjugates (one dye at each end of a PDMS oligomer) using a wide variety of academic and commercially important spirooxazines and naphthopyrans (chromenes). Telechelic conjugates gave faster fade performance per unit length of PDMS oligomer (greater atom efficiency) while having superior matrix compatibility. Independent photochromic switching of different photochromic dye−PDMS conjugates within the same lens matrix was demo...