Dimethylsiloxane Copolymer Research Articles

Preparation and anti-icing performance of cross-linked polysiloxane coatings containing silicone oil

In this work, a cross-linked polysiloxane coating containing silicone oil was prepared via a simple two-component mixing method and the anti-icing performance of the coating was investigated by detecting the ice adhesion force (τice) on the coating. The results of infrared spectroscopy and solvent swelling show that the polysiloxane coating with a certain cross-link density can be prepared by the reaction of methylhydrosiloxane and dimethylsiloxane copolymer and divinyl-terminated polysiloxane, and the cross-link density of the coating can be adjusted by the proportion of polymethylhydrosiloxane (PMHS) and vinyltrimethylsilane (VTMS). The results of ice adhesion force test show that the ice adhesion force on the coating is related to the cross-link density of the coating. With the increase of the cross-link density from 234 ± 43 mol/m3 to 1358 ± 31 mol/m3, the ice adhesion force decreases from 51.15 ± 4.7 kPa to 27.8 ± 3.9 kPa. The lower ice adhesion force corresponds to a higher anti-icing performance. With the addition of silicone oil, the ice adhesion force on the coating can be further reduced to 9.2 ± 1.2 kPa, indicating a further enhancement in the anti-icing performance. The results of icing/deicing cycle test show that, after icing/deicing for 30 cycles, the coating still exhibits efficient anti-icing performance.

Novel Polyimide-block-poly(dimethyl siloxane) copolymers: Effect of time on the synthesis and thermal properties

Polyimide-block-poly(dimethyl siloxane) copolymer was synthesized by a two-step process, initiated by coupling anhydride terminated poly(amic acid), AT-PAA with amino terminated poly(dimethyl siloxane), (NH2)2-PDMS to form poly(amic acid)-block-poly(dimethyl siloxane). The resulting copolymer is then thermally treated to produce polyimide-block-poly(dimethyl siloxane), PI-PDMS. Because of the high glass transition temperature, Tg of polyimide, it is usually cured at a high temperature of about 300°C for over 2.5 h. Copolymerization of polyimide with polysiloxane, reduces the imidization temperature while maintaining high thermomechanical properties. A series of instruments were used to monitor the progress of copolymerization. The time-based analysis of the product of copolymerization enables the optimization of the structure and properties of the copolymers. The chemical structure and composition of the copolymer were studied by Fourier Transform Infrared Spectroscopy, (FT-IR). The incorporation of PDMS blocks into the copolymer and the degree of imidization of the polyimide block increased with increasing reaction time. The change in the viscosity of the copolymerizing solution was monitored by simple shear viscometry conducted with the Brookfield Viscometer. The reported increase in solution viscosity with increasing copolymerization time is associated with increasing molecular weight of the copolymer. The intrinsic viscosity of the copolymer solution was measured as a function of copolymerization time and it was found that the intrinsic viscosity of the copolymer solution increased with increasing reaction time. The glass transition temperature (Tg) and the thermal stability of the copolymer were determined by differential scanning calorimetry, DSC and thermogravimetric analysis, and TGA, respectively. Between 25°C and 420°C, the copolymers synthesized in this study show two glass transition temperatures due to the polyimide, PI block at around 380°C and another peak associated with PDMS plasticized polyimide at about 290–300°C. The two Tg peaks observed in the DSC thermogram are believed to be indicative of the structure of a block copolymer. TGA analysis shows that the thermoxidative stability of the copolymers increased with increasing reaction time, due to the incorporation of increased amount of PDMS unit into the copolymer. The combination of increasing molecular weight of copolymer, higher degree of imidization of polyimide blocks and enhanced thermoxidative stability may translate into improved flame retardancy of copolymers. This suggested enhancement in flame retardancy in air atmosphere, is believed to be due the incorporated PDMS blocks, which can be converted into silica, SiO2, a recognized thermally stable material.

Diphenylsiloxane–dimethylsiloxane copolymer: Optical functions from 191 to 1688 nm (0.735–6.491 eV) by spectroscopic ellipsometry

We report the optical functions of diphenylsiloxane-dimethylsiloxane (DPS-DMS) copolymer as determined from reflection spectroscopic ellipsometry (SE) and transmission ultraviolet-visible data, which were generated over 191–1688 nm from a commercial sample of DPS-DMS. This material is a random, linear copolymer terminated with silanol groups that is a liquid at room temperature and pressure. Both reflection and transmission measurements required special experimental considerations. The reflection SE measurements utilized the “rough-surface” method, wherein the liquid was poured onto a roughened (frosted) glass slide, which scatters the reflected light leaving only the reflection from the liquid surface. That is, there is effectively no substrate or material beneath the liquid that affects the ellipsometry measurements or that needs to be modeled. Transmission measurements were obtained via a dual cuvette approach to eliminate the effects of the cuvettes. The reflection data provided the refractive index across the entire spectral range as well as the extinction coefficient at ultraviolet wavelengths. The transmission measurements provided input for the extinction coefficients at visible and near infrared wavelengths, where the liquid is transparent or semitransparent. The reflected SE data were modeled using a Sellmeier dispersion model and six Gaussian oscillators plus a surface roughness layer. This produced a good fit with a mean squared error (MSE) of 2.41. For example, we obtained the following n(λ) values, where λ is the wavelength in nanometers: n(300) = 1.534, n(500) = 1.477, and n(1000) = 1.458. As expected, the refractive index of DPS-DMS is higher than that of liquid polydimethylsiloxane.

Indium tin oxide and gold nanoparticle solar filters for concentrating photovoltaic thermal systems

The combination of concentrating solar power and photovoltaic technologies in hybrid photovoltaics thermal systems have the potential of increasing the overall efficiency of solar energy by utilizing non-Photovoltaic wavelengths as dispatchable thermal energy for use as industrial process heat and/or electricity generation using a thermal engine. One way of achieving this requires a thermally-stable spectral filter capable of effectively transmitting photovoltaic radiation while absorbing non-Photovoltaic radiation. Here, we utilize indium tin oxide and gold nanoparticles in a silane-based heat transfer fluid capable of withstanding temperatures up to 340 °C while maintaining spectral transparency at photovoltaic wavelengths. To promote compatibility with the heat transfer fluid and achieve greater thermal stability of the nanoparticles, surface modifications were performed for both the indium tin oxide and the gold nanoparticles. It was found that the greatest solution stability was achieved with the use of a (6–7% aminopropylmethylsiloxane)-dimethylsiloxane copolymer surface ligand. Interestingly, when heating the nanoparticles, a spectral blue-shift was observed in the localized surface plasmon resonance peaks of both nanoparticles along with an increase in absorptivity for indium tin oxide. Analysis of the filter performance revealed that a filter optimized for c-Si photovoltaic receiver transmits 73% of bandgap radiation and absorbs 78% of sub-bandgap radiation. The increasing solar absorption properties of the nanoparticle at higher temperatures helped the filter maintained an ideal performance up to 250 °C, even with lower concentrations of nanoparticles. At 300 °C, however, the filter performance reduced due to the disappearance of the gold peak, which is attributed to the inferring free tin ions.

Chemically defined, ultrasoft PDMS elastomers with selectable elasticity for mechanobiology.

Living animal cells are strongly influenced by the mechanical properties of their environment. To model physiological conditions ultrasoft cell culture substrates, in some instances with elasticity (Young's modulus) of only 1 kPa, are mandatory. Due to their long shelf life PDMS-based elastomers are a popular choice. However, uncertainty about additives in commercial formulations and difficulties to reach very soft materials limit their use. Here, we produced silicone elastomers from few, chemically defined and commercially available substances. Elastomers exhibited elasticities in the range from 1 kPa to 55 kPa. In detail, a high molecular weight (155 kg/mol), vinyl-terminated linear silicone was crosslinked with a multifunctional (f = 51) crosslinker (a copolymer of dimethyl siloxane and hydrosilane) by a platinum catalyst. The following different strategies towards ultrasoft materials were explored: sparse crosslinking, swelling with inert silicone polymers, and, finally, deliberate introduction of dangling ends into the network (inhibition). Rheological experiments with very low frequencies led to precise viscoelastic characterizations. All strategies enabled tuning of stiffness with the lowest stiffness of ~1 kPa reached by inhibition. This system was also most practical to use. Biocompatibility of materials was tested using primary cortical neurons from rats. Even after several days of cultivation no adverse effects were found.

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

ABSTRACTThe correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.

Interplay between Mechanical Fatigue and Network Structure and Their Effects on Mechanical and Electrical Properties of Thin Silicone Films with Varying Stoichiometric Imbalance

Thin silicone films for applications as dielectric electroactive polymer (DEAP) are fatigued under mechanical cycling (Wöhler tests) until rupture. The silicones are based on linear vinyl‐terminated poly(dimethylsiloxane) (PDMS) cross‐linked with tetrafunctional methylhydrosiloxane–dimethylsiloxane copolymer. Stoichiometric imbalance of the hydrosilane to vinyl groups is varied (1.3, 1.7, and 3). Complementary, all silicones are compounded with silicone oil (55 wt%) and silica (4.5 wt%). Changes in cross‐linking density, elastic modulus, dielectric permittivity, and dielectric breakdown are examined. The fatigued specimens show increased cross‐linking density due to mechanically induced secondary cross‐linking of excessive hydrosilane groups. This leads to significant changes in the elastic modulus and permittivity of the material, which can negatively affect the performance of the DEAP device. The “critical loading conditions,” where the fatigued specimens show maximum changes in properties, are found to depend on excess hydrosilane content.image

Corrosion protective performance of epoxy-amino branched polydimethylsiloxane hybrid coatings on carbon steel

Purpose – The purpose of this paper was to prepare a hybrid organic/inorganic coating with interesting barrier properties against the corrosion of plain carbon steel sheets in 3.5 per cent NaCl solution. The search for replacing chromates in protective coatings has led to the development of hybrid sol-gel anticorrosive coatings. Appropriate functionalization can dramatically enhance the chemical durability and mechanical strength of these coatings. Design/methodology/approach – To prepare the targeted coating, 1,2-epoxybutane (EB) was mixed with 2 to 4 per cent aminoethylaminopropyl-methylsiloxane dimethylsiloxane (APDMS) copolymer and 1,6-diaminohexane. The above coating (EBAC) has been further mixed with three different corrosion inhibitors “Moly-white® 101-ED, Heucophos Zapp® and cerium ammonium nitrate”, yielding the coatings EBAC-M, EBAC-Z and EBAC-Ce, respectively. The corrosion characteristics of all coatings on the steel panels immersed in 3.5 per cent NaCl solution were obtained using different electrochemical methods such as electrochemical impedance spectroscopic and Tafel polarization measurements. Findings – The newly prepared coatings showed interesting protection properties for protecting the steel substrate against corrosion in chloride-containing media. Originality/value – The results provide a good approach for the modification of polydimethylsiloxane coatings using a simple organic modifier.

Corrosion protective performance of epoxy-amino branched polydimethylsiloxane hybrid coatings on carbon steel

Purpose – The purpose of this work was to prepare a hybrid organic/inorganic coating with interesting barrier properties against the corrosion of plain carbon steel sheets in 3.5 per cent NaCl solution. The search for replacing chromates in protective coatings has led to the development of hybrid sol-gel anticorrosive coatings. Appropriate functionalization can dramatically enhance the chemical durability and mechanical strength of these coatings. Design/methodology/approach – To prepare the targeted coating, 1,2-epoxybutane (EB) was mixed with 2-4 per cent aminoethylaminopropyl-methylsiloxane dimethylsiloxane copolymer and 1,6-diaminohexane. The above coating (EBAC) was further mixed with three different corrosion inhibitors “Moly-white® 101-ED, Hfucophos Zapp®” and Cerium Ammonium Nitrate, yielding the coatings (EBAC-M), (EBAC-Z) and (EABC-Ce), respectively. The corrosion characteristics of all coatings on carbon steel panels immersed in 3.5 per cent NaCl solution were obtained using different electrochemical methods such as electrochemical impedance spectroscopic and Tafel polarization measurements. Findings – The newly prepared coatings showed interesting properties for protecting the steel substrate against corrosion in chloride containing media. Originality/value – The results provide a good approach for the modification of polydimethylsiloxane coatings using a simple organic modifier.

Layer‐by‐layer assembly of halogen‐free polymeric materials on nylon/cotton blend for flame retardant applications

SUMMARYThin films of environmentally safe, halogen free, anionic sodium phosphate and cationic polysiloxanes were deposited on a Nyco (1:1 nylon/cotton blend) fabric via layer‐by‐layer (LbL) assembly to reduce the inherent flammability of Nyco fabric. In the coating process, we used three different polysiloxane materials containing different amine groups including, 35–45% (trimethylammoniummethylphenythyl)‐methyl siloxane‐55‐65% dimethyl siloxane copolymer chloride salt (QMS‐435), aminoethylaminopropyl silsesquioxane‐methylsilsesquioxane copolymer oligomer (WSA‐7021) and aminopropyl silesquioxane oligomers (WSA‐991), as a positive polyelectrolyte. Thermo‐gravimetric analysis showed that coated fabric has char yield around 40% at 600 °C whereas control fabric was completely consumed. The vertical flame test (VFT) on the LbL‐coated Nyco fabric was passed with after flame time, 2 s, and the char length of 3.81 cm. Volatile and nontoxic degradation products of flame retardant‐coated fabric were analyzed by pyrolysis gas chromatography mass spectroscopy (Py‐GCMS). Surface morphology of coated fabrics and burned fabric residues were studied by scanning electron microscopy. Copyright © 2014 John Wiley & Sons, Ltd.

Surface modification of iron oxide (Fe2O3) pigment particles with amino-functional polysiloxane for improved dispersion stability and hydrophobicity

Purpose – The purpose of the present study is to use an amino-functional polysiloxane for the surface modification of red iron oxide (Fe2O3) pigment particles for their improved dispersion stability and hydrophobicity and to study the chemical interactions of polysiloxanes with the particle surface. Design/methodology/approach – Surface-treated red Fe2O3 pigment particles were prepared by treatment of the particles with different quantities of the (aminopropylmethylsiloxane)-dimethylsiloxane copolymer in concentrated suspensions in water. The samples were analysed with different instrumental and spectroscopic techniques to study the interaction of the polysiloxane with the particle surface and the effect of the surface treatment of the particles on their dispersion stability and hydrophobicity. Findings – Chemisorption of the amino-polysiloxane onto the surface of Fe2O3 particles resulted in stable layers which turned out to be helpful in improving greatly the dispersion stability of the particles as shown by the Static Light Scattering and Dynamic Light Scattering results. Formation of a polysiloxane coating onto the surface of the pigment particles was confirmed by studying the interactions of the polymer molecules with Fe2O3 surfaces by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy techniques. Practical implications – The surface-treated red Fe2O3 particles with improved dispersion stability can be important components of various formulations in applications such as the colouring of the cement or inorganic pigment-based paint formulations. Originality/value – The study provides mechanistic insights about the interactions of amino-polysiloxane with the red Fe2O3 particles. The process of surface modification of red Fe2O3 particles with the amino-functional polysiloxane showed increased hydrophobicity and dispersion stability which is an important requirement of the pigment-based formulations in real applications.

Ordering of 6-nm-sized nanodot arrays with 10-nm-pitch using self-assembled block copolymers along electron beam-drawn guide-lines

We studied the possibility to form long-range ordering of self-assembled nanodot arrays with a dot size of 6nm and a dot pitch of 12nm using guide-line templates for ultrahigh-density patterned media. This was realized by using self-assembled block copolymers of polystyrene-poly dimethyl siloxane (PS-PDMS) and the templates made of hydrogen silsesquioxane (HSQ) negative electron beam (EB) resist. We have demonstrated that the method could possibly achieve a minimum pitch of about 10nm using PS-PDMS of molecular weight 7000–1500g/mol and EB-drawn guide lines. These results evidence the promising potential of a technology for achieving 5 Tbit/in2 magnetic storage devices.

Corrosion resistance properties of hybrid organic–inorganic epoxy–amino functionalised polysiloxane based coatings on mild steel in 3·5%NaCl solution

New hybrid organic–inorganic coatings have been developed by reacting a mixture of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraorthosilicate (TEOS) with 2–4% aminoethylaminopropyl-methylsiloxane dimethylsiloxane (APDMS) copolymer as a modifier. The sol–gel polymerisation of the inorganic components was achieved by base catalysation using NaOH. The resultant base coating (CGA) was further modified using two different corrosion inhibitors: Moly-white 101-ED and Hfucophos Zapp yielding coatings (CGA-M) and (CGA-Z) respectively. The corrosion resistant efficiency of these coatings for the protection of mild steel sheets in 3·5%NaCl electrolyte was assessed using AC and DC electrochemical methods, notably, electrochemical impedance spectroscopy (EIS) and DC polarisation scans. Based on the results, the order of corrosion protection of the above coatings was in the order: CGA-M>>CGA-Z>CGA.

Silicone hydrogels based on a novel amphiphilic poly(2‐methyl‐2‐oxazoline)‐b‐poly(dimethyl siloxane) copolymer

A novel amphiphilic hydrogel based on poly(2‐methyl‐2‐oxazoline)‐b‐poly(dimethyl siloxane) (PMeOx–PDMS) block copolymer was developed. First of all, PMeOx–PDMS macromonomer was synthesized by coupling mono‐hydroxylated PMeOx with PDMS followed by end‐capping with methacrylate group. The structures of each step were characterized by NMR and titration. After that, silicone hydrogels were prepared by UV‐initiated copolymerization of PMeOx–PDMS macromonomer with monomers such as 2‐hydroxyethyl methacrylate in the presence of a crosslinker. Measurements of the hydrogels' water contact angle, equilibrium water content, and tensile properties showed that the hydrogels possessed better hydrophilic surface, higher water content, and better ion permeability with the increase of the content of the macromonomer PMeOx–PDMS. Meanwhile, the tensile strength and Young's modulus of the hydrogels decreased slightly. Protein adsorption tests showed that the hydrogels had strong antifouling ability after the incorporation of PMeOx. This newly described hydrogel demonstrated attractive properties to serve as ophthalmic biomaterial. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39867.

Cytotoxicity of nonionic amphiphilic copolymers

The purpose of this study is to ascertain the relationship between the structure of an amphiphilic nonionic polymer and its toxicity for cells (cytotoxicity) growing in a culture. To this end, 16 polymers of different architectures and chemical structures are tested, namely, linear triblock copolymers of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronics); diblock copolymers of propylene oxide, ethylene oxide, and hyperbranched polyglycerol; alternating and diblock copolymers of ethylene oxide and dimethylsiloxane; and two surfactants containing linear (Brij-35) or branched (Triton X-100) aliphatic chains. Polymer-cell interaction is assayed in a culture medium in the absence of serum. Effective concentrations of the polymers causing 50% cell death, EC50, vary within three orders of magnitude. Toxic concentrations of the alternating copolymer, Triton X-100, and Brij-35 are lower than their CMC values. In contrast, all block copolymers, regardless of their chemical structures, become toxic at concentrations above the CMC; that is, they acquire cytotoxicity only in the micellar form. The EC50 values of the copolymers depend on their hydrophilic-liphophilic balance (HLB) through the following empirical formula: EC50 × 106 = 8.71 × HLB2.1. This relationship makes it possible to predict the cytotoxic concentration region of a block copolymer of a known structure.

Optimization of PDMS network for a fast response and sensitive actuation material applied in a MEMS spatial light modulator

The cross-linked networks of linear vinyl-terminated poly(dimethylsiloxane) (PDMS) with trimethylsiloxy-terminated methyhydrosiloxane–dimethylsiloxane copolymer (cross-linker) were investigated by tuning the cross-linker concentration, the chain length of linear PDMS and the functionality of the cross-linker. Response time and elastic modulus of the cross-linked PDMS elastomer were characterized by home-made measurement systems and analyzed based on their network topologies. An optimized PDMS elastomer, which has response time of 9 μs and elastic modulus of 601 kPa, was utilized as the actuation material in a MEMS spatial light modulator (SLM). The fabrication processes were described. This polymer based SLM has shown fast response time (9 μs) and successfully diffracted light into higher orders with 84% first-order diffraction efficiency.

Organic-inorganic hybrid copolymer fibers and their use in silicone laminate composites

Nonwoven organic-inorganic fiber mats of poly(methyl methacrylate)-graft-poly(dimethyl siloxane) copolymers with various PDMS contents were produced by the electrospinning process. The average fibe ...

Synthesis and Characterization of a Poly(dimethylsiloxane)−Poly(ethylene oxide) Block Copolymer for Fabrication of Amphiphilic Surfaces on Microfluidic Devices

A poly(dimethylsiloxane)-poly(ethylene oxide) (PDMS-PEO) vinyl terminated block copolymer has been synthesized via a simple hydrosilylation reaction between hydride-terminated PDMS and PEO divinyl ether. This prepolymer can be subsequently cross-linked into an elastomer in a second hydrosilylation reaction involving a methylhydrosiloxane-dimethylsiloxane copolymer, forming a material suitable for the purposes of fabricating microfluidic devices. The presence of the PEO block in the prepolymer chain results in a much more hydrophilic material following cross-linking. The surface water contact angle of the PDMS-PEO material is 65 degrees +/- 3 (n = 6), as opposed to approximately 110 degrees for native PDMS. Droplets of water straddled by air within molded channels of the PDMS-PEO are concave in shape with contact angles where the fluid meets the side walls of 32 degrees +/- 4 (n = 8), while droplets in PDMS microchannels are more convex with contact angles of 95 degrees +/- 6 (n = 6). The length of the PDMS-PEO prepolymer chain and the multifunctional hydride cross-linker chains appear to dictate the durability of the elastomeric material. Young's modulus measurements yielded values of 0.94 +/- 0.08, 2.6 +/- 0.8, and 1.91 +/- 0.06 MPa for a [5% vinyl excess prepolymer and 10-fold excess of cross-linker], [10% vinyl excess prepolymer and 5-fold excess of cross-linker], and 10:1 PDMS, respectively, confirming that the elasticity of the cross-linked PDMS-PEO is similar to that of PDMS (Sylgard 184:10:1 mixture of elastomeric base to elastomer curing agent). The PDMS-PEO material still possesses enough PDMS character to allow molded channel architectures to be sealed between two pieces of the block copolymer by conformal contact. As a result of the more hydrophilic nature of the material, the channels of devices fabricated from this polymer are self-filling when using aqueous buffers, making it more user-friendly than PDMS for applications calling for background electrolytes void of organic modifiers. Different compositions of PDMS-PEO devices feature different electroosmotic flow values with the 5% vinyl excess prepolymer EOF values of 2.5 +/- 0.7 x 10(-4) and 5.7 +/- 0.8 x 10(-4) cm(2)/(V s) at pHs 6 and 9, respectively, and 1.2 +/- 0.3 x 10(-4) and 2.5 +/- 0.3 x 10(-4) cm(2)/(V s) for the 10% vinyl excess prepolymer device at pHs 6 and 9, respectively.

Interaction of copolymers of dimethylsiloxane and ethylene oxide with model membranes and cancerous cells

Interaction of amphiphilic copolymers and ethylene oxide and dimethylsiloxane with biological membranes is studied. Copolymers are shown to increase the permeability of model membranes. Has been shown that their effect on the permeability of liposomal membranes with respect to dye carboxyfluoresceine correlates with their toxicity. At low nontoxic concentrations, Pluronic L61, a diblock copolymer of dimeth-ylsiloxane and ethylene oxide similar to triblock copolymer of ethylene and propylene oxides, is able to reduce the concentration of chemotherapeutic drug doxorubicin by a factor of 30, which is toxic to cancerous cells stable to remedy drugs.

Extension of the system constants database for open-tubular columns: System maps at low and intermediate temperatures for four new columns

The solvation parameter model is used to characterize the separation properties of four open-tubular columns for gas chromatography at low and intermediate column temperatures covering the range 60–240 °C. Solute descriptors for compounds suitable for characterizing columns over the intermediate temperature range are optimized using an iterative procedure. These compounds, and those previously recommended for the lower temperature range, are used to provide system constant maps for Rxi-5Sil MS, Rxi-17, Rtx-TNT and Rtx-TNT2 columns suitable for merging with a system constants database with entries for more than 50 columns. The Rxi-5Sil MS column is shown to have separation properties similar to the silphenylene–dimethylsiloxane copolymer stationary phase (DB-5ms) but these two columns are not selectivity equivalent. The Rxi-17 column has similar separation properties to the Rxi-50 column but is not selectivity equivalent to it. Rxi-17 is a poly(dimethyldiphenylsiloxane) stationary phase containing 50% diphenylsiloxane monomer and Rxi-50 a poly(methylphenylsiloxane) stationary phase with the same nominal composition but a different monomer structure. The difference in monomer structure results in only small changes in selectivity, and for all but the most demanding separations, the columns are interchangeable. The application-specific column (energetic materials) Rtx-TNT is shown to be selectivity equivalent to columns coated with the poly(dimethyldiphenylsiloxane) stationary phases containing 5% diphenylsiloxane monomer. The Rtx-TNT2 column is selectivity equivalent to the proprietary Rtx-OPPesticides column. Rtx-OPPesticides is a low bleed stationary phase, possibly based on silarylene–siloxane chemistry, with a composition designed to mimic the separation properties of the poly(dimethylmethyltrifluoropropylsiloxane) stationary phases containing 35% methyltrifluoropropylsiloxane monomer. Selectivity equivalence of columns is determined by the statistical agreement in system constants at 20 °C intervals over the full temperature range from 60 to 240 °C, and by the construction of correlation plots for the retention factors of varied compounds for the same temperature intervals.