Polymerization Of Hexamethylcyclotrisiloxane Research Articles

Textile functionalization by combination of twin polymerization and polyalkoxysiloxane‐based sol–gel chemistry

AbstractThe surface modification of textile fibers by coating with nanostructured organic–inorganic hybrid materials is presented. The hydrophobic, solvent resistant and mechanically robust coatings were produced by combining the twin monomer 2,2′‐spirobi[benzo‐4H‐1,3,2‐dioxasiline] (TM) and polyalkoxysiloxanes (silica precursor polymers) in a catalyzed polymerization process. For the application in textile finishing, both aqueous emulsions and ethanolic solutions of mixtures were developed. The precisely adjusted ratio of TM and polyalkoxysiloxanes enabled controlling of the organic and inorganic portions in the hybrid layer. The polymerization process can be advantageously combined with the ring‐opening polymerization of hexamethylcyclotrisiloxane (HMCTS). The resulting ethanolic twin prepolymer solutions and the polyethoxysiloxane emulsions were easy to handle and thus represent a novel and attractive binder for PET surfaces. The coated fabrics were analyzed by means of scanning electron microscopy and X‐ray photoelectron spectroscopy showing hybrid material formation as a homogeneous, sealed surface layer. Improved hydrophobicity as well as resistance to mechanical stress was proven by water droplet‐ and Martindale tests.

Cationic Polymerization of Hexamethylcyclotrisiloxane in Excess Water.

Ring-opening ionic polymerization of cyclosiloxanes in dispersed media has long been discovered, and is nowadays both fundamentally studied and practically used. In this short communication, we show some preliminary results on the cationic ring-opening polymerization of hexamethylcyclotrisiloxane (D3), a crystalline strained cycle, in water. Depending on the catalyst or/and surfactants used, polymers of various molar masses are prepared in a straightforward way. Emphasis is given here on experiments conducted with tris(pentafluorophenyl)borane (BCF), where high-molar polymers were generated at room temperature. In surfactant-free conditions, µm-sized droplets are stabilized by silanol end-groups of thus generated amphiphilic polymers, the latter of which precipitate in the course of reaction through chain extension. Introducing various surfactants in the recipe allows generating smaller emulsions in size with close polymerization ability, but better final colloidal stability, at the expense of low small cycles’ content. A tentative mechanism is finally proposed.

A Green One-pot Synthesis of PDMS Bis-Macromonomers Using an Ecologic Catalyst (Maghnite-H+)

PDMS bis-macromonomers bearing methyl methacrylate end groups is a material mainly used for making extended-wear contact lenses. Silicon-based materials give a good oxygen passage and methyl methacrylate has biocompatibility and mechanical properties of the elastomer. The present study shows the synthesis of this material. The polymerization of hexamethylcyclotrisiloxane (D3) catalyzed by Maghnite-H+ (Mag-H+), a montmorillonite sheet silicate clay exchanged with protons, an efficient catalyst for cationic polymerization of manyheterocyclic and vinylicmonomers. The structural compositions of “Maghnite” have already been determined. The effects of the amount of Mag-H+, temperature and the reaction time were studied. Moreover, we used a simple method, one step in solution to prepare Poly dimethyl siloxane (PDMS) and PDMS bis-macromonomers. The structure of the resulting products is characterized and established by 1H and 13C-NMR, where the methacrylate end groups are clearly visible. The presence of unsaturated end group was also determined by UV and FTIR analysis. The influence of the amount of methacrylic anhydride on monomer conversion was studied. The polymerization yield and the molecular weight of PDMS macromonomers depend on the amount of methacrylic anhydride used.

Polydimethylsiloxane macromonomer bearing N‐vinylcaprolactam as end group: thermosensitive graft copolymers via free radical polymerization

AbstractA polydimethylsiloxane macromonomer was synthesized via anionic ring‐opening polymerization of hexamethylcyclotrisiloxane using N‐vinylcaprolactam anion as initiator and trimethylsilyl chloride as terminating agent. The polydimethylsiloxane macromonomer was copolymerized with N‐vinylcaprolactam in different molar ratios via a free radical mechanism. The new class of graft copolymers thus obtained shows cloud points in water because of an excess of N‐vinylcaprolactam units in the polymer chain. These cloud points can be shifted using randomly methylated β‐cyclodextrin as complexing agent. © 2015 Society of Chemical Industry

Synthesis of poly(dimethylsiloxane)‐containing diblock and triblock copolymers by the combination of anionic ring‐opening polymerization of hexamethylcyclotrisiloxane and nitroxide‐mediated radical polymerization of methyl acrylate, isoprene, and styrene

AbstractPoly(dimethylsiloxane)‐containing diblock and triblock copolymers were prepared by the combination of anionic ring‐opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and nitroxide‐mediated radical polymerization (NMRP) of methyl acrylate (MA), isoprene (IP), and styrene (St). The first step was the preparation of a TIPNO‐based alkoxyamine carrying a 4‐bromophenyl group. The alkoxyamine was then treated with Li powder in ether, and AROP of D3 was carried out using the resulting lithiophenyl alkoxyamine at room temperature, giving functional poly(D3) with Mw/Mn of 1.09–1.16. NMRPs of MA, St, and IP from the poly(D3) at 120 °C gave poly(D3‐b‐MA), poly(D3‐b‐St), and poly(D3‐b‐IP) diblock copolymers, and subsequent NMRPs of St from poly(D3‐b‐MA) and poly(D3‐b‐IP) at 120 °C gave poly(D3‐b‐MA‐b‐St) and poly(D3‐b‐IP‐b‐St) triblock copolymers. The poly(dimethylsiloxane)‐containing diblock and triblock copolymers were analyzed by 1H NMR and size exclusion chromatography. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6153–6165, 2005

Silicone-containing surfactants as templates in the synthesis of mesostructured silicates

Well defined amphiphilic block copolymers containing a polydimethyl siloxane (PDMS) and a poly(ethylene oxide) block (PEO) were synthesized by ring opening polymerization of hexamethylcyclotrisiloxane, followed by chain extension with a PEO block of a defined length. These amphiphilic molecules were used as templates in a solvent-evaporation driven synthesis approach to self-assembled mesostructured silica films. Thin films and powders were prepared, and the resulting material was characterized by X-ray diffraction, transmission electron microscopy, and 29Si and 13C solid state NMR. The behavior of the PEO-b-PDMS block copolymer during heat treatment up to 600°C was followed in detail by solid state NMR.

Synthesis and characterization of (star po1ystyrene)- block - (linear polydimethylsi1oxane)- block -(star polystyrene) triblock copolymers

(Star po1ystyrene)-block-(linear polydimethy1siloxane)-block-(Star polystyrene) triblock copolymers were synthesized by making living Star-shaped polystyrenes through a convergent living anionic polymerization procedure, followed by ring-opening polymerization of hexamethylcyclotrisiloxane (D3) then difunctional coupling. The molecular weights of the resulting polymers were characterized by gel permeation chromatography (GPC), multi angle laser light scattering (MALLS) and 1H NMR spectroscopy. Triblock copolymers with relatively narrow molecular weight distributions were obtained.

Photoinitiated cationic ring-opening polymerization of a cyclosiloxane

Hexamethylcyclotrisiloxane was found to undergo photoinitiated cationic ring-opening polymerization in solution and bulk, upon exposure to UV radiation, in the presence of either sulfonium or iodonium salts or an iminosulfonate derivative. Glass transition temperatures were below −100 °C. Molecular weights, determined by size exclusion chromatography relative to polystyrene standards, increased with photolysis lamp intensity. Use of an iodonium photoinitiator afforded poly(dimethylsiloxane) with Mn=172,000. Polymerization of hexamethylcyclotrisiloxane was accompanied by a small increase in volume (3–4%).

Mechanism of Octamethylcyclotetrasiloxane Polymerization in the Presence of Siloxanediols

Polymerization of hexamethylcyclotrisiloxane (D 3 ) in CH 2 Cl 2 at 30°C, initiated by triflic acid (TfOH) was studied in the presence of siloxanediols (HD 2 OH or HD x OH) which polycondense giving water, or in the presence of water alone for comparison. D represents a siloxane unit OSiMe 2 . In the second case, the relative amounts of cyclic oligomers (D 6 , D 9 ) and of linear high polymer (HP) vary strongly with the molar ratio r = [H 2 O]/[TfOH]. When r increases from 1 to 100 (in homogeneous phase), D 9 /D 6 increases from 0.2 to 2 and D 6 /HP decreases from 1 to 0.3. The large decrease of D 6 amount and the increase in D 9 /D 6 are attributed to the suppression of their formation through oxonium ions and to their exclusive formation, for r > 100, by cyclization of silanol-esters, which is more rapid for HD 9 OTf than for HD 6 OTf. For polymerization of D 3 in the presence of HD 2 OH, there is a fast and limited ring-opening of D 3 (about 10% conversion over 6min) at the beginning, without formation of cyclics (D 6 , D 9 , etc). Then reaction with D 3 stops. Polymerization of HD 2 OH takes place simultaneously, at the same rate as in the absence of D 3 , with slow formation of high polymer. At the end of the polycondensation (after, eg, 4 h) D 3 polymerization starts again, giving D 6 , D 9 , etc, and HP. The inhibition period for D 3 is attributed to the complexation of triflic acid hydrates by silanol groups. These activated silanol groups do not react with D 3 . A comparison of D 3 polymerization with the addition of water, HD 2 OH or HD 15 OH leads to the conclusion that when r is not too large, propagation involves silylester end-groups, but that for large r ratios (100 or higher), it probably occurs mainly on silanol groups reacting with an activated monomer.

Novel silicones for transdermal therapeutic system, 6. Preparation of oligodimethylsiloxane containing 2‐pyrrolidone moiety as a terminal group and its enhancing effect on transdermal drug penetration

AbstractOligodimethylsiloxanes (ODMSs) containing a 2‐pyrrolidone moiety at one chain end were prepared to develop a silicone‐based transdermal penetration enhancer. The 1‐alkyl‐2‐pyrrolidon‐3‐yl group was introduced as a terminal group of ODMS via the initiator method, i.e., the anionic ring‐opening polymerization of hexamethylcyclotrisiloxane was initiated with the silanolate anion derived from (1‐alkyl‐2‐pyrrolidon‐3‐ylmethyl)dimethylsilanol. The disiloxanes were also prepared from the silanol derivatives by reaction with chlorotrimethylsilane. The enhancing activity of drug penetration was evaluated by in vitro experiments using a two‐chamber diffusion cell. Indomethacin and antipyrine were used as model drugs, and the amounts of drugs permeating through the rabbit abdominal skin were measured with and without the ODMSs or disiloxanes. The enhancing activities are influenced by the chain length of the siloxane components and the chemical structure of their end groups. A suitable balance between the hydrophobic ODMS chain and the polar end group might be decisive for a high enhancing activity of drug penetration.

Synthesis and characterization of silicon-containing graft copolymers

Poly(4-t-butoxycarbonyloxystyrene)-g-poly(dimethylsiloxane) and poly(t-butylmethacrylate)-g-poly(dimethylsiloxane) with various chemical compositions were synthesized via free radical polymerization of 4-t-butoxycarbonyloxystyrene (TBCS) or t-butylmethacrylate (TBMA) with silicone macromers. These macromers were prepared by anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D3) and subsequent termination with a chlorosilane compound having a methacrylate functionality. The morphology of the graft copolymer systems was investigated by DSC and TEM.

Equilibria and kinetics of the cationic ring‐opening polymerization of permethylated 1,4‐dioxa‐2,3,5,6‐tetrasilacyclohexane. Comparison with cyclosiloxanes

AbstractEquilibrium constants were determined for the formation of cyclic oligomers of the general formula \documentclass{article}\pagestyle{empty}\begin{document}$ {\hbox{-\hskip-5pt-\hskip-5pt-}[({\rm CH}_3})_2 {\rm Si \hbox{---} Si(CH_3})_2\hbox{---} {\rm O\hbox{-\hskip-6.5pt-}]}_n , n = 2 - 6$\end{document}, in the polymerization of the n = 2 homologue, octamethyl‐1,4‐dioxa‐2,3,5,6‐tetrasilacyclohexane (1). The formation of a linear polymer is thermodynamically favoured in bulk and in concentrated solutions. The equilibrium concentration of cyclics is little dependent on temperature. The six‐membered ring, n = 2, used here as a monomer, is the most abundant cyclic in the equilibrium mixture. Kinetics of the conversion of 1 during the polymerization initiated with CF3SO3H, CH3SO3H and CF3COOH was studied in methylene dichloride solution. In its first stage, the reaction follows first order, but it slows down at higher monomer conversion. The order of the reaction with respect to the acid is two. Some kinetic features of the polymerization initated with CF3SO3H were similar to those exhibited by the polymerization of octamethylcyclotetrasiloxane (D4). In particular small amounts of additional water have rather small effect on the rate, but change to a considerable extent the entropy and enthalpy of activation. The concentration of cyclic oligohomologues passes through a maximum during monomer conversion, which indicates the kinetic enhancement of the cyclisation process. This observation is somewhat similar to those in the polymerization of hexamethylcyclotrisiloxane (D3). However, in contrast to the polymerization of D3 and similarly to the polymerization of D4, the excessive formation of oligomers being multiples of the monomer is not observed.

Novel Silicones for Transdermal Therapeutic System II. Preparation of Oligodimethylsiloxanes Containing Diethyl Phosphoramidate Group at the Chain End and the Evaluation as Transdermal Penetration Enhancers

α-(4-(Diethoxyphosphorimidoyl)butyl)-oligodimethylsiloxane (ODMS-PHOS) was prepared from ODMS containing amino group at the chain end. The prepolymer was synthesized by a ring-opening polymerization of hexamethylcyclotrisiloxane (D3) initiated with lithium trimethylsilanolate, followed by a termination with 3-cyanopropyldimethylchlorosilane and a reduction of the cyano group with lithium alminium hydride. Its enhancing activity on the drug penetration through the skin was studied by in vitro experiment using 2-chamber diffusion cell. All the oligomers effectively enhanced the drug penetration and the permeation coefficients were 4–15 times as much as that without enhancer. The enhancing activity decreased with the increase of the average degree of polymerization. From the detailed analysis of the permeation profile, it was revealed that the partition of the drug from the vehicle to the skin considerably increased, however, diffusivity of the drug in the skin barrier was unchanged as compared with that without enhancer.

New Polymers Derived from Poly(Methylphenylphosphazene)

Abstract The sequential treatment of [Me(Ph)PN]n with n-BuLi and electrophiles such as substituted chlorosilanes, aldehydes and ketones, and carbon dioxide results in new functionalized polyphosphazenes. Graft copolymers have also been prepared by using the anionic polymer intermediate to initiate anionic addition polymerization of styrene, CH2=C(Ph)H, and ring opening polymerization of hexamethylcyclotrisiloxane, [Me2SiO]3.

Synthesis of Polyurethane-Polysiloxane Block Copolymer Having Uniform-Size Poly(dimethylsiloxane) Segments

Abstract A bifunctional living poly(dimethylsiloxane), poly(DMS), was prepared through the anionic ring-opening polymerization of hexamethyl-cyclotrisiloxane (D3) with dilithium salt (2) of bis(p-hydroxydimethylsilyl)phenyl ether (1) as an initiator. The subsequent termination reaction with dimethylchlorosilane followed by the hydrosilation reaction of the end-standing silane function with allyl alcohol produced the uniform-size poly(DMS) with a hydroxypropyl group at both chain ends (4). The polyurethane/polysiloxane block copolymer having uniform-size poly(DMS) segments was then synthesized through the polyaddition reaction of the poly(DMS) having hydroxypropyl groups at both ends (4) with 4,4′-diphenylmethanediisocyanate followed by chain extension with 1,4-butanediol.

The Synthesis of Poly(Dimethylsiloxane-b-Isobutylene-b-Dimethylsiloxane) and Poly-(Dimethylsiloxane-b-Isobutylene-b-Dimethylsiloxane) from Alcohol-Telechelic Polyisobutylenes

Abstract The purpose of these studies was to combine polydimethylsiloxane (PDMS) and polyisobutylene (PIB) sequences into novel triblock, PDMS-b-PIB-b-PDMS, and multiblock, (-PDMS-b-PIB-b-PDMS-)n, copolymers. The key toward syntheses was the definition of conditions for the initiation of living anionic polymerization of hexamethyl-cyclotrisiloxane (D3) at the CH2OLi termini of well-defined tele-chelic PIB sequences. Subsequent deactivation of living D3 polymerization charges with Me3 SiCl yielded the target triblock whereas stoichiometric amounts of Me2 SiCl2 gave the multiblock copolymer.

The anionic oligomerization of hexamethylcyclotrisiloxane with methylmethoxysilanes

The polymerization of hexamethylcyclotrisiloxane (D3) initiated with inorganic and organometallic bases was studied in the presence of methylmethoxysilanes of general formula (MeO)nSiMe4−n (n = 1, 2, 3 or 4) as chain transfer agents. In the case of n = 2, 3 or 4, the process can proceed in a specific way leading to the predominant formation of linear oligomers composed of sequences of structure [(Me)2SiO]3 (monomer unit) and fragments of one molecule of the methylmethoxysilane. The reaction provides a good method for synthesis of some of these oligomers. The mechanism of the oligomerization is discussed.

The influence of trimethylsilanol on the polymerization of hexamethylcyclotrisiloxane by the action of sodium trisilanolate

The influence of trimethylsilanol (TMS) on the polymerization of hexamethylcyclotrisiloxane (D 3) under the action of sodium trimethylsilanolate (TMSN) has been studied. It has been shown that as the molar ratio [TMS] 0 : [TMSN] 0 = α increases, the activity of the TMSN, the activation energy and the pre-exponential factor of the Arrhenius equation are all increased. The influence of the TMS is due to breakdown of associates of TMSN and to the formation of associates of TMSN with TMS. TMS participates directly in the reaction due to interaction with D 3 and its polymerization products.

Polymerization of hexamethylcyclotrisiloxane by α,ω-bis-(tetramethylammonium) oligodimethylsiloxanolate in the presence of trimethylsilanol

A study was made of the role of trimethylsilanol (TMS) in polymerization of hexamethylcyclotrisiloxane (D 3) by the action of α,ω-bis-(tetramethylammonium) oligodimethylsiloxanolate. In the presence of TMS as a result of solvation of silanolate groups by silanol groups complexes are formed which are characterized by a lower activation energy E a of polymerization D 3 than α,ω-bis-(tetramethylammonium) oligodimethylsiloxanolate. In addition to copolymerization with D 3 TMS takes part in homocondensation and co-condensation with the siloxanols formed, which take place at a much lower rate than copolymerization. Homo- and co-condensation are only observed in those cases when [TMS] 0>[D 3] 0, co-condensation predominating with high conversions of D 3. When [TMS] 0⩽[D 3] 0 initial rates of consumption of TMS and D 3 are the same.

Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. I. Nature of polymerization

AbstractPolymerization behavior of hexamethylcyclotrisiloxane (D3) in toluene solution with the use of benzyltrimethylammonium bis(o‐p;henylenedioxy)phenylsiliconate as a catalyst, dimethyl sulfoxide as promoter, and adventitious moisture as initiator was investigated. The polymerization system gives a linear difunctional polymer, HO(Me2SiO)xH, with a molecular weight which is inversely proportional to the amount of water reacted rather than to the amount of catalyst employed. The polymerization in the presence of H2O gives rise to molecular weight distributions very close to Poisson distributions. The normalized experimental GPC curve agrees very well with the theoretical GPC curve calculated from the polymerization scheme: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm H}_2 {\rm O} + ({\rm Me}_2 {\rm SiO})_3 \to {\rm HO}({\rm Me}_2 {\rm SiO})_3 {\rm H}} \\ {{\rm HO(Me}_{\rm 2} {\rm SiO)}_{\rm 3} {\rm H} + {\rm N(Me}_{\rm 2} {\rm SiO)}_{\rm 3} \to {\rm HO}({\rm Me}_2 {\rm SiO})_{3(n + 1)} {\rm H}} \\ \end{array} $$\end{document} Polymerization carried out in the combined presence of H2O and ROH, where R is Me or Me3Si, gives rise to bimodal molecular weight distributions. The resulting polymers consist of HO(Me2SiO)2xH and RO(Me2SiO)xH. The molecular weight of the former is twice that of the latter, and their proportion depends on the ratio of H2O to ROH. The system is a special type of “living” polymer.