Polysiloxane Copolymers Research Articles

Conjugation in polysiloxane copolymers via unexpected Si-O-Si dπ-pπ overlap, a second mechanism?

Conjugation in polysiloxane copolymers via unexpected Si-O-Si dπ-pπ overlap, a second mechanism?

Effect of flame‐retardant melamine and dispersants on the mechanical, thermal, and foaming properties of flexible polyurethane foam

AbstractThe objective of this study was to investigate the effect of adding flame‐retardant melamine and five different dispersants on the precipitation, foaming, mechanical, and thermal properties of flexible polyurethane foam (FPUF). Precipitation experiments were conducted to analyze the effect of dispersant on the separation of flame retardant and polyol, and the foaming characteristics of polyurethane (PU) foam after adding dispersant were analyzed. The effect of adding a dispersant on mechanical strength was characterized by measuring tensile strength, tearing strength, and hardness, and scanning electron microscopy analysis was performed to analyze morphological characteristics. Thermogravimetric analysis (TGA) was performed to analyze the thermal properties of PU foam. A horizontal flame test, limiting oxygen index test, and cone calorimeter tests were conducted to examine the flame retardancy of PU foam with flame retardant melamine and dispersant added. The dispersant ANTI‐TERRA‐U is a solution of a salt of unsaturated polyamine amides and low‐molecular acidic polyesters. And, the dispersant BYK‐220S is a solution of a low molecular weight, unsaturated acidic polycarboxylic acid polyester with a polysiloxane copolymer. The dispersants ANTI‐TERRA‐U and BYK‐220S improved the density, tensile strength, tear strength, and hardness of FPUF. TGA of the top and bottom portions of the foam showed less weight difference for samples containing dispersants, indicating better homogeneity due to improved dispersibility. Therefore, we conclude that dispersants are beneficial additives to improve the mechanical properties and dispersibility of PU foam.

Improving thermal and chemical stabilities of electronic epoxies using polysiloxane copolymers - Part I: core-shell particles

Improving thermal and chemical stabilities of electronic epoxies using polysiloxane copolymers - Part I: core-shell particles

Fabrication of gradient multilayer polymer with improved damping performance based on poly(butyl acrylate)-grafted polysiloxane

A linear polysiloxane copolymer (PSI) was synthesized via hydrolysis of three siloxane monomers followed by hydrolytic condensation. Then, butyl acrylate monomers were used for grafting and cross-linking PSI copolymer under photoinitiation. The resulting poly(butyl acrylate)-grafted polysiloxane (PBA-g-PSI) exhibited different morphologies and microphase separation structures by varying the weight ratio of PSI and PBA. Inspired by the gradient structure of biological materials, a novel gradient multilayer polymer was prepared by assembling different PBA-g-PSI layers. The unique microstructure of gradient multilayer polymer and microphase separation of PSI showed enhanced damping performance such as high tan δmax and low damping temperatures. In addition, the thermal stability and thermo-mechanical property with damping mechanisms of these gradient multilayer polymers were also studied.

Hydrogen blast led to deaths at silicone plant

Leaking and uncontained hydrogen led to an explosion this past May that killed four workers and seriously injured a fifth at AB Specialty Silicones in Waukegan, Illinois, according to a preliminary investigation report released Dec. 18, 2019, by the US Chemical Safety and Hazard Investigation Board (CSB). The hydrogen explosion took place in an area where the company was making a silicon hydride emulsion called EM 652, according to the CSB. EM 652 and a raw material used to make it, a methylhydrogen polysiloxane copolymer called XL10, can produce explosive amounts of hydrogen gas under certain conditions, the CSB says. The EM 652 was held in a tank that was neither sealed nor vented to a safe location. The building was also not equipped with functioning detectors for hydrogen or other flammable gases. While the building filled with flammable vapors, the workers attempted to open the emulsion area to outside

Crosslink network and phenyl content on the optical, hardness, and thermal aging of PDMS LED encapsulant

ABSTRACTThis work aims to synthesize new series of polysiloxane copolymer through hydrosilylation reaction based on different level of crosslink densities and phenyl content. The results revealed that polysiloxanes resins with phenyl rings increased viscosity up to 3800 cps while displaying a relatively high refractive index of 1.531. The asymmetric phenyl substitution onto chain backbone led to formation of densely packed structure resulting in reduced water absorption and gas permeability of PDMS resins. High level of crosslinking contributed to a high shore A hardness and adhesion strength. It displayed transparency of 97% whose percentage reduction was 1.6% under thermal and 0.6% UV aging. No obvious discoloration was observed during accelerated thermal aging up to 210 min at 80 °C. These results are key attributes that make the synthesized polysiloxane series as ideal candidate for high brightness LED encapsulant. © 2019 Wiley Periodicals, Inc. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47895.

Investigation of the Effects of Non-Conjugated Co-Grafts on the Spectroelectrochemical and Photovoltaic Properties of Novel Conjugated Graft Copolymers Based on Poly(3-hexylthiophene).

A new type of polysiloxane copolymers, with conjugated–regioregular poly(3-hexylthiophene) (P3HT) and non-conjugated-poly(ethylene glycol) (PEG)-grafts have been synthesised, and their properties have been studied alongside those of the parent conjugated polymer (P3HT). Spectroelectrochemical and conductometric analyses revealed an early rise of the conductance of the polymers. Once spectral changes begin taking place, the conductance is stable, implying a loss of mobility of charge carriers, even though standard doping/dedoping patterns are observed. Prototype bulk heterojunction solar cells have been fabricated, based on P3HT/[6,6]-Phenyl-C61-butyric acid methyl ester (PCBM), as well as by substituting P3HT for each of the copolymers. The prototype solar cells achieved PCEs of up to 2.11%. This is one of the highest reported power conversion efficiency (PCE) for devices based on P3HT with low average molecular weight Mn = 12 kDa. Strong correlation between the structure of the copolymer and its photovoltaic performance was found. Elongation of PEG copolymer chain and the use of methyl group instead of terminal hydroxyl groups significantly improved photovoltaic performance.

Synthesis and Luminescence Properties of a Novel Eu3+‐Containing Polysiloxane Copolymer

AbstractThrough pre‐coordination and subsequent polymerization from vinyl‐functionalized complex monomer with polysiloxane prepolymer (synthesized by vinyltrimethoxysilane and diphenylsilanediol), a novel anti‐ultraviolet Eu3+‐containing polysiloxane copolymer was obtained. FT‐IR spectra and UV/Visible absorption spectra prove the structure of the copolymer. TG‐DTG analyses indicate the copolymer keeps stable up to 321°C. When excited at 365 nm, the copolymer exhibits a stronger red emission at 612 nm. And the CIE coordinates (x=0.648, y=0.336) are very close to the National Television Standard Committee standard. Further, the red LEDs fabricated with the copolymer on 365 nm‐emitting chips display superior luminance (52110 cd/m2). Finally, 30‐day UV aging test only shows luminance loss of 6% and power efficiency loss of 7.3%, so the UV‐aging resistance of the copolymer is realized. All the results indicate that the Eu3+‐containing organosilicon copolymer is a promising anti‐ultraviolet red candidate.

Dendrite-free Li metal deposition in all-solid-state lithium sulfur batteries with polymer-in-salt polysiloxane electrolyte

Replacement of solid polymer electrolyte (SPE) to routine liquid electrolyte is highly desirable for high-energy-density lithium sulfur batteries due to its low volatility, high safety and the ability to suppress shuttle effect. Herein, a polymer-in-salt polysiloxane SPE was fabricated with bi-grafted polysiloxane copolymer, lithium bis(trifluoromethanesulfonyl)imide and poly(vinylidene fluoride), which shows higher ionic conductivity (7.8 × 10-4 S cm-1 at 25 °C). To obtain the satisfactory ionic conductivity and high mechanical property of solid electrolyte simultaneously, cellulose acetate matrix was combined as a rigid substrate to prepare composite polymer electrolyte (CPE) that possesses high ionic conductivity (4.0 × 10-4 S cm-1), enhanced mechanical strength (6.8 MPa), wide electrochemical stability window (4.7 V vs. Li+/Li), and high ion transference number (0.52) at ambient temperature. In addition, the CPE effectively inhibits the growth of lithium dendrites and diffusion of polysulfides. The assembled lithium sulfur battery with CPE exhibits good room-temperature cycling performance at 1C, which indicates that such polymer-in-salt polysiloxane based composite electrolyte membranes can be applied to ambient temperature all-solid-state lithium sulfur batteries.

Self-organization processes in polysiloxane block copolymers, initiated by modifying fullerene additives

Thin films of a polyblock polysiloxane copolymer and their composites with a modifying fullerene C60 additive are studied by atomic force microscopy, Rutherford backscattering, and neutron scattering. The data of atomic force microscopy show that with the addition of fullerene to the bulk of the polymer matrix, the initial relief of the film surface is leveled more, the larger the additive. This trend is associated with the processes of self-organization of rigid block sequences, which are initiated by the field effect of the surface of fullerene aggregates and lead to an increase in the number of their domains in the bulk of the polymer matrix. The data of Rutherford backscattering and neutron scattering indicate the formation of additional structures with a radius of 60 nm only in films containing fullerene, and their fraction increases with increasing fullerene concentration. A comparative analysis of the data of these methods has shown that such structures are, namely, the domains of a rigid block and are not formed by individual fullerene aggregates. The interrelation of the structure and mechanical properties of polymer films is considered.

Surface hydrophobization of polyester fibers with poly(methylhydro-dimethyl)siloxane copolymers: Experimental design for testing of modified nonwoven materials as oil spill sorbents

This paper reports on the hydrophobization of polyester fibrous nonwoven with poly(methylhydro-dimethyl)siloxane copolymers in order to produce water-repellent sorbents for oil spill cleanup. Polysiloxane copolymers were first synthesized and characterized prior to be used as hydrophobization agents. The produced hydrophobic sorbents were characterized by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX); infrared spectra (FTIR) and water-contact angle measurements (WCA). Nonwoven sorbents were evaluated for oil sorption in pure oil bath and in the presence of water (W-test). A statistical experiment design was employed for materials testing and the development of data-driven models. The optimal hydrophobic nonwoven yielded maximal sorption capacities equal to 5.52 g/g and 10.03 g/g for dodecane and motor oil uptake, respectively. The mechanism of oil attachment on polymeric fibers was investigated by optical microscopy revealing a key role of inter-fiber voids for oil retention. Centrifugation tests demonstrated a high recycling ability of spent nonwoven sorbents.

Efficient hydrosilylation reaction in polymer blending: An original approach to structure PA12/PDMS blends at multiscales

An in situ amide hydrosilylation reaction was developed to prepare polyamide 12 (PA12)/polysiloxane copolymers by reactive blending. This reaction is focused on the addition of hydrogenosilane groups (SiH) from polysiloxane to the carbonyl group from the PA12 amide function. To evidence this carbonyl hydrosilylation onto an amide based polymer, an approach on model compounds (use of N-methylpropionamide) was carried out. The mechanism and kinetics were investigated with multinuclear NMR (1H, 13C and 29Si). During kinetics studies, the concentration of N-silylated copolymers can reach 70 mol% after 2 h reaction at 100 °C.Amide hydrosilylation reaction was extended to the reactive blending of polyamide 12 with PDMS-SiH under molten processing conditions. Formation of a structured blend was investigated by rheology and electronic microscopy at different scales. The impact of both shearing and reaction on the final morphology was deeply studied and the interfacial enhancement by compatibilization was confirmed. As a result, the dispersion of PDMS domains decreased from 3 to 4 μm to around 0.8 μm in diameter forming submicronic morphology. Furthermore, it was possible to control the dispersion of PDMS at different scales by modifying the physico-chemical parameters (molar mass and functionality) of both components.

Bacterial membranes are the target for antimicrobial polysiloxane-methacrylate copolymer.

Antibacterial polysiloxane polymers with pending tert-butylamine groups are a novel class of compounds that are compatible with silicone elastomers, but their mechanism of action is not well understood. The research into their action mechanism was conducted on a polysiloxane copolymer grafted with tert-butylaminoethyl methacrylate and covalently attached fluorescein. Fluorometric measurements results suggest that the polymer forms a stable link with bacteria. The results of β-galactosidase enzyme assay with the use of ortho-nitrophenyl-β-galactoside as a substrate show that the polymer has a damaging effect on bacterial membranes. The scanning and transmission electron micrographs of Escherichia coli cells incubated with the polymer prove further that the polymer’s site of action is bacterial cell membranes. In order to investigate the polymer interaction with bacterial membranes the fluorescein labelled polymer was incubated with bacterial cells and membranes isolation and identification method was next applied. The E. coli membrane fractions were identified by light scattering, protein content, oxidase NADH activity and N-phenylnaphtylamine fluorescence measurements, as well as electron microscopy. Oxidase NADH and N-phenylnaphtylamine were the inner membrane markers. The bacterial membranes were then tested for the presence of the polymer. The experiments gave evidence that the copolymer binds to the inner bacterial membrane. Further studies, where the copolymer was incubated with isolated mixed (inner and outer) membrane fractions, proved that the copolymer exerts more destructive effect on E. coli outer membrane. The damaging effect on the membranes is concentration dependent.

Thermally controlled silicone functionalization using selective Huisgen reactions

The thermal azide–alkyne cycloaddition using electron deficient alkynes has previously been applied to the room temperature crosslinking of polysiloxanes. However, only propiolates were used as the alkyne partner to functionalize polysiloxanes under metal-free conditions. Herein, we extend the methodology to alkynes with differing electronic demands and therefore different reactivities, which opens the possibility for selective silicone functionalization using sequential reactions simply by changing temperatures. To obtain a more thorough understanding of the effect of the alkyne electron density on the cycloaddition, differential scanning calorimetry was used to determine the temperature at which triazole formation is initiated for a variety of alkynes. The study showed acetylene dicarboxylates to have the lowest onset cycloaddition temperature of those studied, 37°C. By contrast, propargyl esters only began to react at 101°C, with other carbonyl-modified alkynes showing intermediate reactivity. Benzyl azide was used to demonstrate that the silicone copolymers bearing pendant propiolate alkynes could be reacted preferentially at lower temperatures, but only just, over the more electron rich terminal propiolamide alkynes. By contrast, the reaction of silicone propiolates with benzyl azide occurred nearly specifically in the presence of terminal propargyl alkynes on a polysiloxane copolymer containing both groups.

High temperature stationary phase of polysiloxane containing N,N′-bis(diphenylsilyl) tetramethylcyclodisilazane for gas chromatography

A polysiloxane copolymer (P(BPTMC)-alt-ODMS) containing N,N′-bis(diphenyl-silyl) tetramethylcyclodisilazane (BPTMC) was used as stationary phase in gas chromatography with high thermal stability.

1 H and 29Si NMR Spectroscopy as a Powerful Analytical Tool to Evaluate the Activity of Various Platinum-Based Catalysts in Model Olefin Hydrosilylation

The structure of polysiloxane copolymers obtained by hydrosilylation of 1-octene with polymethylhydrosiloxane (PMHS) was analyzed by 29Si NMR spectroscopy and revealed a tendency to form block copolymers. Although all the platinum catalysts that were used showed a tendency to form some block structures, only Karstedt catalyst led to well defined block copolymers. However, the tacticity of these copolymers could not be determined using Heteronuclear Multiple Bond Correlation (HMBC) 2D (1H/ 29Si) NMR technique. The following criteria were found to affect the structure of the hydrosilylation product: low SiH conversion, the “age” of the Karstedt catalyst (low TON) and high octene/SiH ratios.

A dielectric relaxometry study of segmental dynamics in PDMS/boron composite and hybrid elastomers

In this work, the motional dynamics and relaxation behavior of a series of model poly(dimethylsiloxane)-co-meta-carborane (PDMS-co-CB) hybrid elastomers have been studied in depth, using Broadband Dielectric Spectrometry over a temperature range of −130 to 100 °C and a frequency window of 10−1 to 107 Hz. The segmental α-relaxation of both the PDMS and carborane chain segments has been characterized at specific carborane backbone incorporation levels. A direct correlation between the ratio of PDMS to carborane segments and the motional constraint of the network as a whole was observed. In addition to the study of the α-motional modes associated with local intra-segmental motions and the onset of cooperative motion, we have also identified and studied a higher order cooperative (normal-mode) motion of extended segments of the carborane–siloxane co-polymer chains at elevated temperatures. These normal mode motions have been shown to follow an Arrhenius temperature dependence, are sensitive to the local chemical environment and have not been previously reported in this class of polysiloxane copolymer. The motional dynamics of the PDMS-co-CB networks have been compared and contrasted with those of a series of conventionally filled PDMS–Boron Nitride (PDMS–BN) composite systems. While the effects of the chemically bound carborane segment on the PDMS chain dynamics, local order and global network properties have been shown to be directly correlated, significant and predictable, the effects of the BN filler on the PDMS matrix are significantly less so and the results suggest that the filler material may in fact be disrupting the network order, with a consequently negative impact on the properties of the composite.

Synthesis and properties of block and graft waterborne polyurethane modified with α,ω‐bis(3‐(1‐methoxy‐2‐hydroxypropoxy)propyl)polydimethylsiloxane and α‐N, N‐dihydroxyethylaminopropyl‐ω‐butylpolydimethylsiloxane

In this study, α,ω‐bis(3‐(1‐methoxy‐2‐hydroxypropoxy)propyl)polydimethylsiloxane and α‐N,N‐dihydroxyethylaminopropyl‐ω‐butylpolydimethylsiloxane were used to prepare block and graft waterborne polyureathane–polysiloxane copolymer dispersions. α,ω‐bis(3‐(1‐methoxy‐2‐hydroxypropoxy)propyl)polydimethylsiloxane was synthesized by hydrosilylation, methoxylation and equilibrium reactions; α‐N,N‐dihydroxyethylaminopropyl‐ω‐butylpolydimethylsiloxane was synthesized via hydroxyl protection, alkylation, anionic ring‐opening polymerization, hydrosilylation, and deprotection. Block and graft waterborne polyurethane–polysiloxane copolymer dispersions were prepared by the reaction of poly(propylene glycol) (PPG), toluene diisocyanate (TDI), 2,2‐dimethylol propionic acid (DMPA), 1,4‐butanediol (BDO), α,ω‐bis(3‐(1‐methoxy‐2‐hydroxypropoxy)propyl)polydimethylsiloxane, and α‐N,N‐dihydroxy‐ethylaminopropyl‐ω‐butylpolydimethylsiloxane. The water absorption of block and graft waterborne polyurethane–polysiloxane copolymer films decreased from 163.9 to 40.2% and 17.3%, respectively, when percent of polysiloxane (w/w) increased from 0 to 5%, and the tensile strength of the block waterborne polyurethane–polysiloxane copolymer films decreased while the tensile strength of graft waterborne polyurethane–polysiloxane copolymer films increased with increase of percent of polysiloxane. For graft waterborne polyurethane–polysiloxane films, the tensile strength would decrease when percent of polysiloxane was more than 3%. POLYM. ENG. SCI., 54:805–811, 2014. © 2013 Society of Plastics Engineers

Preparation and characterization of a new microwave immobilized poly(2-phenylpropyl)methylsiloxane stationary phase for reversed phase high-performance liquid chromatography

A new reversed phase high-performance liquid chromatography (RP-HPLC) stationary phase was prepared and its chromatographic and physical–chemical properties were evaluated. The new stationary phase was prepared with a silica support and poly(2-phenylpropyl)methylsiloxane (PPPMS), a phenyl type polysiloxane copolymer. Since this is a new copolymer and there is little information in the literature, it was submitted to physical–chemical characterization by infrared spectroscopy and thermogravimetry. The chromatographic phase was prepared through sorption and microwave immobilization of the copolymer onto a silica support. The chromatographic performance was evaluated by employing test procedures suggested by Engelhardt and Jungheim, Tanaka and co-workers, Neue, and Szabó and Csató. These test mixtures provide information about the hydrophobic selectivity, silanophilic activity, ion-exchange capacity, shape selectivity and interaction with polar analytes of the new Si-PPPMS reversed phase. Stability tests were developed using accelerated aging tests under both basic and acidic conditions to provide information about the lifetime of the packed columns.

Polyimide-b-polysiloxane Copolymers: Synthesis and Properties

This review discusses the synthesis, structure and properties of polyimide-b-polysiloxane copolymers. Polysiloxane modified polyimides has become an important class of materials over the past 20 years because of their ease of processing and interesting properties. Although polyimides are widely used in engineering applications because of their outstanding mechanical properties and thermal stability, their processability, toughness, and adhesion can be significantly enhanced by incorporation of polysiloxanes. The synthesis of polyimide-b-polysiloxane copolymers is performed by a one-step copolymerization method or a two-step method, resulting in a wide range structures and thermo-mechanical properties. The initial modulus and thermal stability of polyimide-b-linear polysiloxane copolymers can be further improved by copolymerization with ladder-like polysiloxanes which possess outstanding thermal stability and mechanical properties. The study of synthesis and properties of polyimide-b-polysiloxane copolymers is essential because it provides a useful insight into the processing-structure–property relationship.