Dimethylsiloxane Units Research Articles

Increased stability of polymer dispersions obtained by heterophase radical polymerization of styrene and MMA in the presence of water-insoluble organosilicon macromeres

It is shown that during the copolymerization of methyl methacrylate with the surfactant comonomer α,ω-dipropylmethacrylatep olidimethylsiloxane with the number of repeating dimethylsiloxane units n = 20 (DPMPDMS), strong interfacial adsorption layers are formed on the surface of polymer–monomer particles formed from microdrops, ensuring the stability of particles to various types of influences.

Fast synthesis of high molecular weights polydiethylsiloxanes and random poly(dimethylsiloxane-co-diethylsiloxane) copolysiloxanes via cyclic trimeric phosphazene base catalyzed ring-opening (co)polymerization

Polysiloxanes containing diethylsiloxane units with unique low temperature flexibility have been widely applied under extreme conditions in many fields. However, the synthesis of polydiethylsiloxane (PDES) and its copolymers was challenging due to the easy accessible polymerization-depolymerization equilibrium between linear propagating chains and cyclosiloxane byproducts in the ring-opening polymerization (ROP) of hexaethylcyclotrisiloxane (D3Et) and the large reactivity gaps among different cyclosiloxanes in the copolymerization. In this work, PDESs were successfully prepared via cyclic trimeric phosphazene base (CTPB) catalyzed ROP at room temperature in high yields. The ROP of D3Et proceeded efficiently with low CTPB loading (low to 0.01 mol%) and the resulting PDES homopolymers had high molecular weights (up to 404.0 kg/mol). Moreover, poly(dimethylsiloxane-co-diethylsiloxane) (PMES) random copolymers with tunable diethylsiloxane contents (20 ∼ 87 mol%) can be directly prepared via ring-opening copolymerization (ROCP) of D3Et and octamethylcyclotetrasiloxane (D4) using CTPB as catalyst within 5 min at ambient temperature. The reactivity ratio of D3Et (r = 1.04) and D4 (r = 0.89) suggested the comparable reactivity between D3Et and D4 to ensure their random copolymerization characteristics, thus proving the unique high efficiency of CTPB catalyst applied here. Microstructure characterizations of the PMES copolymers by 1H and 29Si NMR verified the controlled copolymer composition and the random distribution of diethylsiloxane and dimethylsiloxane units. The thermal property investigations by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicated the good low-temperature flexibility and thermal stability of PMES copolymers, displaying great potential in extreme environmental applications.

A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

AbstractA following new interpretation of apparent induction period is proposed considering the experimental results obtained: octamethylcyclotetrasiloxane (D4) is activated by the reaction with acid to generate an activated derivative (A4). A4 reacts with D4 to generate A8, an active species containing eight dimethylsiloxane units. A8 backbites to generate mostly A4 and D4, which causes retardation in polymerization, but occasionally to form A3 and D5. A3 is highly reactive, and when the concentration of A3 exceeds a certain limit, much Ai where i is large enough is formed and promotes fast growth of chain at the interfacial area due to high concentration of D4. The interpretation assumes that A3 accelerates growth of chain faster than other species, and that A8 tends to backbite rather than grow. The interpretation is supported by the experimental results of polymerization conducted with D4 and D3, or D5 and D3 charged.

New Poly(carboranylmethyldiorganosiloxane)s and Vulcanizates Based on Them

New high-temperature resistant poly(carboranylmethyldiorganosiloxane)s have been synthesized by the polycondensation of 1,7-bis-[hydroxy(dimethyl)silylmethyl]-m-carborane with bis-(dimethylamino)diorganosilanes. It has been shown that the replacement of dimethylsiloxane units in polymer chain by methylphenylsiloxane or diphenylsiloxane units leads to formation of amorphous polymers. The polymers show high thermal stability and resistance to alkaline reagent. Thermally stable and fire resistant vulcanizates showing high strength within –40 to +300°C (in air) have been obtained from the poly(carboranylsiloxane)s.

Polymers with regular alternation of 1,7-bis[(dimethyl)silylmethylene]-m-carborane and diorganosiloxane units

New high-thermostable carboranylmethyl-containing diorganosiloxane polymers have been obtained by polycondensation of equimolar amounts of 1.7-bis[hydroxy(dimethyl)silylmethylene]-m-carborane with bis(dimethylamino)diorganosilanes. It was shown, that in the case of replacement of 24 to 33 mol. % of dimethylsiloxane units with methylphenylsiloxane or diphenylsiloxane units with bulk phenyl groups, only amorphous polymers are formed. The polymers are highly soluble in organic solvents and have high thermostability.

Microphase Separation in Poly(Imide Siloxane) Copolymer

The comparative analysis of microheterogeneous structure of the surface of films of amorphous aromatic polyetherimide: poly[4, 4'-bis(4''-N-phenoxy)diphenylsulfon]imide of 1,3-bis(3', 4-dicarboxyphenoxy)benzene (PEI) and poly(imide siloxane) block copolymer (PSI) containing PEI blocks and blocks of dimethylsiloxane units was performed according to electron microscopy. It was shown that anisotropy, long-range order, and the correlation length of density fluctuations increase in PSI film as compared to PEI. PSI samples are characterized by asymmetrical biaxial surface texture, as opposed to PEI, which exhibits axial texture. Periodic density oscillations are observed along the directions of axes of PSI structure at the micron scale. The obtained results evidence microphase separation in PSI film caused by spatially oriented contact interactions between the blocks of dimethylsiloxane units.

Effect of Molecular Structure on the CO2 Separation Properties of Hydrophobic Solvents Consisting of Grafted Poly Ethylene Glycol and Poly Dimethylsiloxane Units

This work describes the preparation of a set of nine new novel hydrophobic PEG-substituted solvents. These solvents include linear, T-shaped, and disubstituted conformations of the PEG grafted with PDMS molecule. The effect of changing both the molecular conformation and length of PEG side arm on the physical properties and CO2 absorption capacity was studied. These solvents are intended for separation of CO2 and H2 in precombustion CO2 capture and are intended to replace the current-state-of-the-art glycol-based solvents and operate at a higher temperature. The properties of the disubstituted solvents are exceptionally well suited for precombustion CO2 capture applications because of their hydrophobicity, high CO2 solubility, low evaporation rate, and lack of foaming.

Микрофазовое разделение в имидсилоксановом сополимере

By means of electron microscopy, a comparative analysis of the micro-inhomogeneous structure of the surface of films of amorphous aromatic polyetherimide — poly{4,4'-bis[(4''-N-phenoxy) diphenylsulfone] imide 1,3-bis (3',4-dicarboxyphenoxy) benzene} (PEI) - and imidosiloxane block copolymer (PSI) containing blocks of PEI units and blocks of dimethylsiloxane units. It is shown that in the PSI film, compared with PEI, the anisotropy, long-range order, and the correlation length of density fluctuations increase. The PSI sample has an asymmetrical biaxial surface texture, unlike PEI, which is characterized by an axial texture. In the direction of the axes of the PSI texture on a micron scale, periodic density oscillations are observed. The results obtained indicate microphase separation in the PSI film due to spatially oriented contact interactions between the blocks of dimethylsiloxane units.

Structure-property interplay of asymmetric membranes comprising of soft polydimethylsiloxane chains and hard silica nanomaterials

Silica nanomaterials modified with monomolecular C18-alkyl silane or oligomeric dimethylsiloxane units were loaded in-situ during the formation of PDMS membrane. The small-angle neutron scattering (SANS) study was performed to probe structural compatibility between the modified silica and PDMS. The Ornstein-Zernike (OZ) and Debye-Anderson-Brumberger (DAB) models were excellently fit to the SANS data describing nanoscale structure morphology in terms of correlation length scales of the soft and hard segmental units. The polymeric chain was stretched or contracted depending upon the type and amount of silica incorporation. This indicated limiting amount of silica incorporation in the PDMS membrane structure depending upon structural compatibility between the silica and PDMS. The C18-alkyl silylated silica was found to be the best compatible with the membrane structure. The membrane with 30% (w/w) C18-alkyl silylated -silica loading exhibited the best performance in pervaporation separation of alcohol/water.

Hydrophobic, amorphous metal–organic network readily prepared by complexing the aluminum ion with a siloxane spaced dicarboxylic acid in aqueous medium

ABSTRACTA less common dicarboxylic acid with siloxane spacer, 1,3‐bis(carboxypropyl)tetramethyldisiloxane, whose structure is for the first time determined crystallographically, is used to coordinate aluminum through an environment‐friendly preparation process, resulting in a polymeric structure of amorphous metal–organic framework (aMOF) type. The high flexibility of the spacer induced by the siloxane bond gives the polymeric product a glass transition slightly below room temperature, while the long length of the former creates the premises for collapse of the network and consequently reduced porosity. At the same time, the high hydrophobicity of the tetramethyldisiloxane fragment and its low surface energy, which causes it to migrate to the air interface, gives the network low moisture sorption capacity guaranteeing the stability of its properties in a wet environment. The particulate complex, of the order of 1–200 nm, as generated by the synthesis, proves to be suitable as filler for silicone with outstanding reinforcement effect, without significantly affecting their transparency. The presence of the dimethylsiloxane units in the structure of both the matrix and the filler ensures good incorporation of the latter without the need for special compatibility treatments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47144.

Improving the Resolution of Kendrick Mass Defect Analysis for Polymer Ions with Fractional Base Units.

The concept of a fractional base unit for the Kendrick mass defect (KMD) analysis of polymer ions is introduced for the first time. A fraction of the ethylene oxide (EO) repeat unit (namely EO/8) has been used for the KMD analysis of a poly(ethylene oxide) and found to amplify the variations of KMD between monoisotopic and 13C isotopes, producing an isotopically resolved KMD plot at full scale when the KMD plot computed with EO is fuzzy. The expansion of the KMD dimension using a fractional base unit has then been successfully used to unequivocally discriminate all the distributions from a blend of poly(ethylene oxide)s in a high resolution KMD plot calculated with EO/3 as base unit. Extending the concept of fractional base units to other repeat units, the visualization of the co-oligomers from a poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer has been dramatically improved using a fraction of the propylene oxide repeat unit (namely PO/3) in an oligomer and isotope resolved plot. High resolution KMD plots were eventually calculated from tandem mass spectra of poly(dimethylsiloxane) ions using a fraction of the dimethylsiloxane (DMS) unit (namely DMS/6) with clearer point alignments and a discrimination of all the product ion series, out of reach of the KMD analysis using DMS. Versatile and producing high resolution KMD plots, the introduction of fractional base units is believed to be a major step towards the implementation of the KMD analysis as a routine data mining tool for mass spectrometry in polymer chemistry.

Diffusion-Induced Hydrophilic Conversion of Polydimethylsiloxane/Block-Type Phospholipid Polymer Hybrid Substrate for Temporal Cell-Adhesive Surface.

In this study, diffusion-induced hydrophobic-hydrophilic conversion of the surface of the cross-linked polydimethylsiloxane (PDMS) substrate was realized by employing a simple swelling-deswelling process of PDMS substrate in a block-type polymer solution with the aim of development of a temporal cell-adhesive substrate. The ABA block-type polymer composed of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) segment and PDMS segment with over 70% of dimethylsiloxane unit composition could be successfully incorporated in the PDMS substrate during the swelling-deswelling process to prepare the PDMS/phospholipid block copolymer hybrid substrates. During the aging process of the PDMS substrate for 4 days in aqueous medium, its surface property changed gradually from hydrophobic to hydrophilic. X-ray photoelectron spectroscopy and atomic force microscopy data provided strong evidence that the time-dependent hydrophilic conversion of the PDMS/block-type phospholipid polymer hybrid substrate was induced by the diffusion of the hydrophilic PMPC segment in the block-type polymer to be tethered on the substrate. During the hydrophilic conversion process, surface-adsorbed fibronectin was gradually desorbed from the substrate surface, and this resulted in successful detachment of two-dimensional connected cell crowds.

Physical Properties and Microphase Separation of Polyurethane Films Containing Poly(dimethyl siloxane) Component

Polyurethanes (PUs) containing poly(dimethyl siloxane) (PDMS) unit in soft segment, PU-Si, were syn- thesized, and their mechanical properties and phase separation were investigated. Various amounts of PDMS units were incorporated into PU via a solution polymerization method in N,N'-dimethylformamide using poly(tetramethylene ether glycol) and PDMS diol as a soft segment and methylene diphenyl diisocyanate and 1,4-butanediol as a hard segment. Two series of PU-Si samples with an HS content of 23% and 32% were prepared and analyzed. Results showed that the elongation-at-break of the PU-Si films increased, breaking stress decreased, and the hydrophobicity of the film increased as the PDMS content in PU-Si increased. SAXS analysis indicated that the microphase separation of the PU-Si film between hard and soft segments decreased with increasing PDMS content, irrespective of the HS content.

Synthesis and physical properties of poly(l‐lactic acid)‐poly(dimethyl siloxane) multiblock copolymers prepared by direct polycondensation

ABSTRACTMultiblock copolymers consisting of poly(l‐lactic acid) and poly(dimethyl siloxane) were prepared by the polycondensation of oligo(l‐lactic acid) (OLLA) with dihydroxyl‐terminated oligo(dimethyl siloxane) and dicarboxyl‐terminated oligo(dimethyl siloxane). Copolymers with number‐average molecular weights of 18,000−33,000 Da and various content ratios of oligo(dimethyl siloxane) (ODMS) unit were obtained by changing the feed ratio of these oligomers. A film prepared from the copolymer with an ODMS content ratio of 0.37 exhibited two independent peaks at −107°C and 37°C in the mechanical loss tangent for temperature dependence, suggesting the formation of microphase separation between the OLLA and ODMS segments. The film had a tensile strength of 3.2 MPa and a high elongation of 132%. The film also exhibited a high strain recovery even after repeated straining. The incorporation of dimethyl siloxane units as multiblock segments was confirmed to improve the flexibility of poly(l‐lactic acid). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40211.

Optimization of sol–gel/pyrolysis routes to silicon oxycarbide glasses

The optimization of the synthesis of silicon oxycarbide ceramics via the sol–gel/pyrolysis route is described, starting from several alkylalkoxysilanes and vinylalkoxysilanes. The main aim was to achieve low weight losses during cure and pyrolysis and also a compact ceramics morphology. The theoretical composition of the pyrolysates was changed between SiO1.5C and SiO1.2C2.3, by varying monomer types and ratios. An assessment of the real composition was performed using energy-dispersive X-ray spectroscopy. The smallest weight losses were obtained for the resins based on vinyltriethoxysilane and dimethyldiethoxysilane which were additionally modified by the addition of a small amount of boric acid. Somewhat higher weight losses combined with the best toughness were found for resins based on non-vinylated silsesquioxane with a low content on linear dimethylsiloxane units. As an alternative, a precursor (SiO0.9C2.8) was prepared via hydrosilylation, based on cyclic dimethylsiloxane oligomers interconnected to a network, but its weight losses were higher than those of sol–gel silicon oxycarbide.

Effect of UV/ozone irradiation on the surface properties of electrospun webs and films prepared from polydimethylsiloxane–urea copolymers

Highly hydrophobic surfaces of silicone–urea copolymers were transformed into hydrophilic ones upon UV/ozone treatment. The extent of surface modification was strongly dependent on the sample preparation method and the exposure time. The physical and chemical changes at the copolymer surfaces were analyzed by spectroscopic (XPS, ATR-FTIR), microscopic (SEM) techniques and static water contact angle measurements. ATR-FTIR spectra clearly showed the dramatic change in the strongly hydrogen bonded urea hard segments and the degradation of dimethylsiloxane units in silicone–urea copolymers. XPS results revealed the formation of SiOx on the surface, which gradually increased with exposure time. After 3h of UV/ozone exposure, Si(2p) binding energy shifted from 101.9 to 102.85eV, which is a clear indication of an increase in the oxidation state of silicon. The deterioration of microroughness of the electrospun webs upon UV/ozone exposure, which was revealed by SEM, resulted in a dramatic decrease in the static water contact angle values from 129 to 62°. These results clearly show that UV/ozone process is a very simple and facile method to transform hydrophobic silicone–urea copolymer surfaces into fairly hydrophilic ones.

Synthesis of High Molecular Weight Poly (1, 1, 12, 12-tetramethyl-13-oxa-1, 12-disilatridecanylene-co-dimethylsiloxane) Using Anionic Ring-opening Polymerization

High molecular weight copolymers, referred to as polysilalkylene siloxanes or hybrid silicones, were prepared using anionic ROP of 1,1,3,3,14,14,16,16-octamethyl-2,15-dioxa-1,3,14,16-tetrasilacyclohexacosane (II) and octamethylcyclotetrasiloxane (D4) mixtures. The resultant gum-like polymers were characterized by 1H NMR, 13C NMR, 29Si NMR, FTIR, GPC, TGA and FTIR. It was determined that the resultant polymers possessed a ratio of alkylene to dimethylsiloxane units similar to that expected from the original monomer ratio. Number averaged molecular weights ranged from 111,000 to 160,900 g/mol in yields of 75% to 78%. In addition, the thermal stability of the poly(decanylene-co-dimethylsiloxane)s were similar to that of the homopolymer based on II.

Quick and simple modification of a poly(dimethylsiloxane) surface by optimized molecular design of the anti-biofouling phospholipid copolymer

The optimal molecular design of an amphiphilic copolymer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and dimethylsiloxane (DMS) units for modifying a poly(dimethylsiloxane) (PDMS) surface in a quick and simple manner was developed. Block- and random-type copolymers with three different compositions were each coated on a PDMS surface in a protic solution. The resulting surfaces were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, contact angle measurement. From the results, the random-type copolymer containing 86% hydrophobic DMS unit was the most suitable molecular design to be stably coated on the PDMS surface. From view point of bioengineering application, it was confirmed that for optimal suppression of protein adsorption and cell adhesion on a PDMS surface, the surface should be coated by immersing it in the polymer solutions with a concentration of 30 mg mL−1 for more than 30 s.

Temperature-Dependent Vapor Pressure of Selected Cyclic and Linear Polydimethylsiloxane Oligomers

The isothermal retention times of seven cyclic (D4 to D10) and nine linear (L5 to L13) dimethylsiloxane oligomers on a nonpolar gas chromatographic column were determined at temperatures between (308.15 and 438.15) K. Using normal alkanes as standard reference and calibration compounds, these retention times were used to derive liquid state vapor pressures at 298.15 K as well as enthalpies of vaporization that allow for the estimation of vapor pressures over a wide range of temperatures. The data agree within 0.25 log units with vapor pressure values previously reported by Flaningam (1986) but extend those values to lower temperatures and larger oligomers. Cyclic dimethylsiloxanes are more volatile than linear dimethylsiloxanes of a similar size. Oligomers with 10 and more dimethylsiloxane units are expected to sorb appreciably to aerosol at environmentally relevant temperatures.

High Hole Mobility for a Side‐Chain Liquid‐Crystalline Smectic Polysiloxane Exhibiting a Nanosegregated Structure with a Terthiophene Moiety

Side-chain liquid-crystalline siloxane polymers bearing terthiophene moieties as mesogenic pendant groups have been synthesized. An alkenylterthiophene derivative was treated with poly(hydrogenmethylsiloxane) and poly(dimethylsiloxane-co-hydrogenmethylsiloxane)s in Me(2)SiO/MeHSiO ratios of 1:1 and 7:3, respectively, in the presence of the Karstedt catalyst, to produce pale yellow polymers. The degrees of introduction of the mesogenic unit were 100, 50, and 30%, respectively. The polymers exhibit ordered smectic phases at room temperature. The copolymers with dimethylsiloxane units form smectic phases as a consequence of nanosegregation between the mesogenic units and siloxane backbones with the alkylene spacers. Time-of-flight measurement reveals that the hole mobility exceeds 1×10(-2) cm(2) V(-1) s(-1) in the ordered smectic phase of the copolymer with a degree introduction of the mesogenic units of 50%. This value is comparable to that of the highly ordered mesophases of low-molecular-weight derivatives of phenylnaphthalene and terthiophene. Because of the segregation behavior induced by the flexible backbone, a closer molecular packing structure favorable for fast carrier transport may be formed in the smectic phase of the copolymer in spite of the low density of the mesogenic groups.