Carbosilane dendrimers based on siloxane polymer

A method for synthesizing growth ring‐type dendritic macromolecules starting from siloxane polymer with Si H bonds [Me₃SiO(MeSiOH)_nSiMe₃] as the core and dichlorovinylsilane, dichloromethylsilane, lithium phenylacethylide, and allylmagnesium bromide as the building blocks is described. The siloxane polymer was produced to the second dendritic generation by the repetition of hydrosilation and alkenylation as well as by an alkynylation process. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 724–729, 2000     

Synthesis and characterization of phosphonate‐containing polysiloxanes

Phosphonate‐functionalized polysiloxanes have been prepared with a new siloxane/phosphonate monomer. The reaction of 3‐chloropropylmethyldimethoxysilane with trimethylphosphite or triethylphosphite produces several new monomers containing pendant phosphonate groups. Copolymerization with dimethyldimethoxysilane has produced polymers soluble in most organic solvents. The acid hydrolysis of the phosphoryl esters has produced hydrophilic siloxane polymers containing phosphonic acid groups. The thermal properties of the polymers and several related small molecules have been compared with thermogravimetric analysis. Both the monomers and the resulting polymers have been characterized with ¹H, ¹³C, ³¹P, and ²⁹Si NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 48–59, 2003     

Phototriggered atmospheric degradation of poly[methyl(phenyl)silanediyl] in the presence of ultraviolet absorbers

Oxidative changes in poly[methyl(phenyl)silanediyl] (PMPSi) films exposed in a Weather-O-Meter ATLAS Ci 3000+ were monitored by Fourier transform infrared spectroscopy. Increases in absorption in the siloxane, carbonyl, and hydroxyl regions, decreases in absorption in the Si Si region, and changes in the aromatic C H bond region were monitored. Experiments in argon and air indicated the key role of oxygen in the process. The photooxidation of PMPSi was retarded by triazine- and oxalanilide-based ultraviolet absorbers [2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)phenol and N-(4-tert-butyl-2-ethoxyphenyl)-N′-(2-ethylphenyl)oxalanilide] protecting the polymer by the excited-state intramolecular proton-transfer mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 714–721, 2004     

Kinetics and mechanism of the formation of poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene] and poly(methyldecylsiloxane) by hydrosilylation

The kinetics of the formation of poly(carbosiloxane), as well as of alkyl-substituted poly(siloxane), by Karstedt's catalyst catalyzed hydrosilylation were investigated. Linear poly(carbosiloxane), poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene], (PTMDSE), was obtained by hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS) and 1,1,3,3-tetramethyldisiloxane (TMDS), while alkyl-substituted poly(siloxane), poly(methyldecylsiloxane), (PMDS), was synthesized by hydrosilylation of poly(methylhydrosiloxane) (PMHS) and 1-decene. To investigate the kinetics of PTMDSE formation, two series of experiments were performed at reaction temperatures ranging from 25 to 56 °C and with catalyst concentrations ranging from 7.0 × 10⁻⁶ to 3.1 × 10⁻⁵ mol Pt/mol CHCH₂. A series of experiments was performed at reaction temperatures ranging from 28 to 48 °C, with catalyst concentrations of 7.0 ×10⁻⁶ mol of Pt per mol of CHCH₂, when kinetics of PMDS formation was investigated. All reactions were carried out in bulk, with equimolar amounts of the reacting Si H and CHCH₂ groups. The course of the reactions was monitored by following the disappearance of the Si H bands using quantitative infrared spectroscopy. The results obtained showed typical first order kinetics for the PTMDSE formation, consistent with the proposed reaction mechanism. In the case of PMDS an induction period occurred at lower reaction temperatures, but disappeared at 44 °C and the rate of Si H conversion also started to follow the first-order kinetics. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2246–2258, 2007     

Macroscopic–microscopic mechanical relaxation behavior of hybrid organic–inorganic materials

The mechanical properties of transparent hybrid organic–inorganic nanocomposites made from siloxane and zirconium oxopolymers are investigated at two different length scales. The complex interface that associates the two phases is made of covalent Zr O Si bonds and hydrogen bonding. The rubbery properties studied by creep and recovery present specific behaviors in comparison with model elastomers. This is a result of the complex crosslinking units. The stress relaxation phenomenon has been studied at the molecular scale by ²H quadrupolar NMR. During stress relaxation, the anisotropy of the molecular motion decreases slowly. This study demonstrates the straightforward relationship existing between the macroscopic and microscopic relaxation phenomena. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 645–650, 2001     

One‐Step Growth of ca. 2–15 nm Polymer Thin Films on Hydrogen‐Terminated Silicon

Here we show direct polymer growth on hydrogen‐terminated silicon (Si H) as a one‐step process. Si H is immersed in a heated solution of an initiator, a monomer, and a crosslinker. The resulting polymer films are 2–15 nm thick, the thickness can be tuned by varying reaction conditions, and the polymer films are robust. Thinner films are obtained in polymer growth without crosslinker. Radicals produced by the initiator and in growing polymer chains may pluck H atoms from Si H to make reactive dangling bonds. These in turn appear to react with monomers and crosslinkers. Crosslinkers tethered through one double bond may be grafted into polymer chains growing in solution. Surface reactivity is demonstrated by optical ellipsometry, X‐ray photoelectron spectroscopy, atomic force microscopy, and wetting.

     

Surface study of ladderlike polyepoxysiloxanes

By using the two‐liquid geometric method and the three‐liquid acid‐base method, we are the first to determine the surface tensions of ladderlike polyepoxysiloxanes by the measurement of contact angles on thin films. Three kinds of ladderlike polymers have been synthesized: A C (which has the alkyl group and the epoxy group graft to the ladderlike polysilsesquioxane chain), A C P (which has the alkyl group, phenyl group, and epoxy group graft to the ladderlike chain), and A P (which has the phenyl group and epoxy group in the ladderlike side chain). The results showed that when different liquids and different theories are chosen to determine the surface energies, there are some minor differences in the values but a similar trend is still exhibited. The surface energies of these three polymers are in the following order of γ_{SA C} < γ_{SA C P} < γ_{SA P}. Interestingly, the surface energy increases for these polymers are mainly from the nonpolar part of the polyepoxysiloxanes. XPS surface analysis indicated that the Si and O ratios of these polymers at the air‐polymer interface were in the order of A C > A C P > A P, suggesting Si atoms were more likely to migrate to the polymer surface and the bulky effect of the phenyl groups could also interfere with the migration of the Si atoms. As a result, Si and O ratio at the interface determines the order of apparent surface energy for these three polymers. Experimental data also reflect that there are differences between the ladderlike polyepoxysiloxanes and the commercially available linear polysiloxanes. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 138–147, 2000     

Solid polymer electrolytes I,preparation, characterization,and ionic conductivity of gelled polymer electrolytes based on novel crosslinked siloxane/poly(ethylene glycol) polymers

A series of crosslinked siloxane/poly(ethylene glycol) (Si–PEG) copolymers were synthesized from the reactive methoxy‐functional silicone resin (Si resin) and PEGs with different molecular weights via two kinds of crosslinking reactions during an in situ curing stage. One of the crosslinking reactions is the self‐condensation between two methoxy groups in the Si resin, and another one is an alkoxy‐exchange reaction between the methoxy group in the Si resin and the OH group in PEG. The synthesized crosslinked copolymers were characterized by Fourier transform infrared spectroscopy, DSC, and ¹³C NMR. The crosslinked copolymers were stable in a moisture‐free environment, but the Si? O? C linkages were hydrolyzed in humid conditions. The gel‐like solid polymer electrolytes (SPEs) were prepared by impregnating these crosslinked Si–PEG copolymers in a propylene carbonate (LiClO₄/PC) solution. The highest conductivity reached 2.4 × 10^?4 S cm^?1 at 25 °C and increased to 8.7 × 10^?4 S cm^?1 at 85 °C. The conductivities of these gel‐type SPEs were affected by the content of LiClO₄/PC, the molecular weights of PEGs, and the weight fraction of the Si resin. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2051–2059, 2004     

Synthesis of poly(phosphonosiloxane) and its cyclic monomer via hydrosilylation and phosphonylation of vinylbenzyl chloride

Phosphonylation of polysiloxane and cyclosiloxane oligomers is described. Hydrosilylation of vinylbenzyl chloride (VBC) with a poly(methylhydrosiloxane), or its cyclic monomer, followed by phosphonylation with triethyl phosphite leads to the production of stable phosphonosiloxanes that are characterized by  Si C and  C P bonds. The polymer, which is a liquid with a glass transition temperature of −38.3 °C, is soluble in alcohols and an alcohol and water mixture. The phosphonylated siloxanes dissolve and chelate uranyl nitrate and transition metal salts. The hydrosilylation of VBC yields α and β isomers:  Si CH₂ CH₂ and  Si CH(CH₃); the ratio between these two depends upon the type of solvent and the reaction conversion. A kinetic study of the hydrosilylation reaction of VBC suggests a second order in respect to the reactants. The reaction rate is dependent upon the catalyst concentration and temperature. Hydrosilylation of vinylbenzyl phosphonate could not be accomplished with the platinum (complex) catalyst; this is attributed to the presence of phosphoryl groups that are strong electron donors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4043–4053, 1999     

A new controllable approach to synthesize hyperbranched poly(siloxysilanes)

A new controllable approach to synthesize hyperbranched poly(siloxysilanes) via hydrosilylation of A₂‐ and B′B_x‐type monomers was developed in this work. A₂ monomers (dimethylbis(dimethylsiloxy)siloxane and tetramethyldisiloxane), B′B_x monomers (methylvinyldiallylsilane and vinyltriallylsilane), and the resultant hyperbranched poly(siloxysilanes) were well characterized using FTIR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, and SEC/MALLS. The In situ FTIR results indicate that the controllable polymerization can be carried out quickly and the reaction process was obviously performed in two stages. At the first stage, silicon hydride selectively reacts with vinyl silane groups, which produces intermediate structures with one Si? H and two (or three) allyl groups. Consequently, at the second stage, these intermediates act as new AB₂ (or AB₃) type monomers and continue to be self‐polymerized to generate hyperbranched polymers. By this novel controllable approach, molecular weights and their polydispersity of the resulted hyperbranched poly(siloxysilanes) can be conveniently regulated via adjusting the process parameters, such as feeding ratio of two monomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2708–2720, 2008     

Dual capacitor technique for measurement of through‐plane modulus of thin polymer films

Polymer thin films are widely used as coatings and interlevel dielectrics in microelectronic applications. In thin‐film structures, stresses are generated due to interaction with adjacent layers and film shrinkage due to solvent evaporation or curing. This causes polymer chain orientation resulting in anisotropic (direction dependent) film properties. The dual capacitor technique has been developed to measure in situ, the through‐plane (z) stress‐strain behavior of thin polymer films. A parallel plate capacitor device and an interdigitated electrode structure were used as sensors to detect changes in dielectric permittivity and thickness of thin polymer films under compression. The analytical and finite element models used to interpret the capacitance measurements have been presented. The Clausius–Mossotti equation was used to determine the volume change in the film from the permittivity measurements. Results have been reported for 10–14 μm thick, Cyclotene 4026‐46 benzocyclobutene films and 10–12 μm thick films of polyimide PI‐2611. The Cyclotene 4026‐46 films were found to be mechanically isotropic, whereas the PI‐2611 films were highly anisotropic. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1634–1644, 2000     

Photoinitiated polymerization of aryl cyclic sulfonium salts

Polymers are produced by direct photolysis of substituted aryl cyclic sulfonium Zwitterionic salts in solution or film. Analysis of zwitterionic monomers via ¹³C NMR, UV, and IR spectroscopy as well as X‐ray diffraction clearly identifies the structures taking part in the photoinduced polymerization in the solid crystalline films. The protonated form of the zwitterionic monomers, however, fails to produce detectable amounts of polymer upon photolysis under any conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 571–584, 2001     

Synthesis,characterization, and stability of carbodiimide groups in carbodiimide‐functionalized latex dispersions and films

Cyclohexylcarbodiimidoethyl methacrylate (CCEMA) and t‐butylcarbodiimidoethyl methacrylate (t‐BCEMA) were prepared in a two‐step synthesis. These monomers were then used to prepare carbodiimide‐functionalized PBMA and PEHMA latex particles, employing two‐stage emulsion polymerization, with the carbodiimide–methacrylate monomers being introduced only in the second stage under monomer‐starved conditions. During emulsion polymerization, the carbodiimide moiety ( NCN ) was found to be unstable at pH 4, but stable when the pH of the dispersion was increased to 8, using NaHCO₃ as the buffer. Survival of  NCN group against hydrolysis during the polymerization, and during storage in the dispersion, was enhanced by using EHMA as the comonomer (more hydrophobic) and the t‐butyl carbodiimide derivative. The t‐butyl group provides more steric hindrance to the hydrolysis reaction. A decrease in the reaction temperature from 80°C to 60°C was also found to increase the extent of  NCN group incorporation during emulsion polymerization. Under ideal conditions, more than 98% of the  NCN groups in the monomer feed are successfully incorporated into the latex. When these latex particles are mixed with a  COOH containing latex and allowed to dry, polymer diffusion leading to crosslinking occurs. Films annealed at 60°C reach a gel content of 60% in 10 h. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 855–869, 2000     

Characterization of thin polymer‐like films formed by plasma polymerization of methylmethacrylate: A neutron reflectivity study

The microstructure of the plasma‐polymerized methylmethacrylate (ppMMA) films is characterized using neutron reflectivity (NR) as a function of the plasma reaction time or film thickness. Variation in the crosslink density normal to the substrate surface is examined by swelling the film with a solvent, d‐nitrobenzene (dNB). In the presence of dNB, uniform swelling is observed throughout the bulk as well as at the air surface, and silicon oxide interfaces. The results indicate that the MMA film prepared by plasma polymerization (ppMMA) has a uniform crosslink density from air surface to substrate surface. Additionally, the scattering length density of the plasma‐polymerized MMA film (SLD ≈ 0.750 × 10⁻⁶ Å⁻²) is much lower than that of a conventional PMMA film (SLD = 1.177 × 10⁻⁶ Å⁻²). The increase in film thickness following dNB sorption is 7.5% and at least 36% for the ppMMA and PMMA films, respectively. This suggests that the films formed by plasma polymerization are different from conventional polymers in chemical structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2522–2530, 2004     

Thermally reversible covalently bonded linear polymers prepared from a dihalide monomer and a salt of dicyclopentadiene dicarboxylic acid

Alkali and earth‐alkali salts of dicyclopentadiene dicarboxylic acid (DCPDCA) were prepared and employed as monomers in the polyesterification with an α,ω‐dihalide monomer, such as 1,4‐dichlorobutane (DCB), 1,4‐dibromobutane (DBB), α,α′‐dichloro‐p‐xylene (DCX), and α,α′‐dibromo‐p‐xylene (DBX). Novel linear polymers that possessed repeating moieties of dicyclopentadiene ( DCPD ) in the backbone were thus prepared. The IR and NMR spectra indicated that poly(tetramethylene dicyclopentadiene dicarboxylate) (PTMDD) with a number‐average molecular weight (M_n ) of about 1× 10⁴ and poly(p‐xylene dicyclopentadiene dicarboxylate) (PXDD) with a M_n of 4–6 × 10³ were obtained with an yield of about 80% via the polyesterification of the alkali salts with DBB and DCX, respectively. The reaction was carried out in the presence of a phase transfer catalyst, such as BzMe₃NBr or poly(ethylene glycol), in DMF at 100 °C for 4 h. Oligomers with a lower M_n (1–2 × 10³) were obtained when the earth‐alkali salts were employed as salt monomers. Compared to the irreversible linear polymers, poly(p‐xylene terephthalate) (PXTP) and poly(p‐xylene maleate) (PXM), prepared through the reaction between DCX and the potassium salts of terephthalic and maleic acid, respectively, the specific viscosities (η_sp) of the new linear polymers increased abnormally with the decrease of the temperature from 200 °C to 100 °C. This occurred due to the thermally reversible dedimerization/redimerization of  DCPD moieties of the backbone of the polymers via the catalyst‐free Diels–Alder/retro Diels–Alder cycloadditive reactions. The ratio of the η_sp at 100 °C and 200 °C of the reversible polymers was found to be much higher than that of PXTP and PXM, even when the heating/cooling cycle was carried out several times under a N₂ atmosphere. The obtained results indicated that thermally reversible covalently bonded linear polymer can be obtained by introducing the  DCPD structure into the backbone of the polymer through the polymerization of a monomer containing the  DCPD moiety. The reversible natures of the polymers and oligomers might be useful in preparing easily processable and recyclable polymers and thermosensor materials. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1662–1672, 2000     

Differential scanning calorimetry (DSC) and Raman spectroscopy study of poly(dimethylsiloxane)

Poly(dimethylsiloxane) was studied by laser Raman spectroscopy and differential scanning calorimetry. The Si O Si skeletal mode at 489 cm⁻¹ and the C Si C deformation bands at 188 cm⁻¹ and 158 cm⁻¹ were studied as functions of temperature from ambient to −130°C, and effects of temperature interpreted in accordance with results from thermal analysis. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2805–2810, 1998     

Silicon‐terminated telechelic oligomers by ADMET chemistry: Synthesis and copolymerization

Methoxydimethylsilane and chlorodimethylsilane‐terminated telechelic polyoctenomer oligomers (POCT) have been prepared by acyclic diene metathesis (ADMET) chemistry using Grubbs' ruthenium Ru(Cl₂)(CHPh)(PCy₃)₂ [Ru] or Schrock's molybdenum Mo(CH CMe₂Ph)(N 2,6 C₆H₃ i Pr₂)(OCMe(CF₃)₂)₂ [Mo] catalysts. These macromolecules have been characterized by FTIR, ¹H‐, ¹³C‐, and ²⁹Si‐NMR spectroscopy. The molecular weight distributions of these polymers have been determined by GPC and vapor pressure osmometry (VPO). The number‐average molecular weight (M_n) values of the telechelomers are dictated by the initial ratio of the monomer to the chain limiter. The termini of these oligomers (M_n = 2000) can undergo a condensation reaction with hydroxy‐terminated poly(dimethylsiloxane) (PDMS) macromonomer (M_n = 3300) [HO Si(CH₃)₂ O { Si(CH₃)₂O }_x  Si(CH₃)₃], producing an ABA‐type block copolymer, as follows: (CH₃)₃SiO [ Si(CH₃)₂O ]_x [ CHCH (CH₂)₆ ]_y [ OSi(CH₃)₂ ]_x OSi(CH₃)₃. The block copolymers were characterized by ¹H‐ and ¹³C‐NMR spectroscopy, VPO, and GPC, as well as elemental analysis, and were determined by VPO to have a M_n of 8600. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 849–856, 1999     

Polycondensation of trialkoxysilane monomers accelerated by neighboring group participation of urea moiety

(Phenylaminomethyl)trimethoxysilane (= α‐amino‐siloxane) was treated with various isocyanates to obtain a series of siloxanes having urea moieties (= α‐urea‐siloxanes). Their hydrolysis‐condensation reactions were monitored with ²⁹Si NMR, to reveal that they exhibited much higher reactivity than a urea‐siloxane derived from [3‐(phenylamino)propyl]trimethoxysilane (= γ‐amino‐siloxane). When compared with the derivation of the γ‐amino‐siloxane into the corresponding γ‐urea‐siloxane, those of the α‐amino‐siloxane into the corresponding α‐urea‐siloxanes were accompanied by much larger shifts of the ²⁹Si NMR signal toward a higher magnetic field. These results suggested that the location of the urea moiety in the α‐urea‐siloxanes was favorable to its intramolecular coordination to the silicon atom to exhibit its “neighboring group participation” that promoted transformation of the tetravalent silicon center into the pentavalent one, which is more electrophilic to make the siloxanes more susceptive to undergo the hydrolysis and condensation reactions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6654–6659, 2008     

Synthesis of ladder polymers containing polydiacetylene backbones connected with methylene chains and their optical properties

The polymers consisting of polydiacetylene (PDA) backbones were obtained from the novel monomer derivatives, R CC CC R′ CC CC R [where R =  (CH₂)₄OCONHCH₂COOC₄H₉, R′ =  (CH₂)_n ; n = 2, 4, 8] [4BCMU4A(n)], in which linear methylene chain is sandwiched between two diacetylene moieties by solid-state 1,4-addition reaction. The polymerization process was investigated in detail by using spectroscopic techniques such as solid-state ¹³C-NMR, visible absorption, and IR absorption spectra. It was estimated that the polymerization of 4BCMU4A(8) and 4BCMU4A(4) takes place by two consecutive 1,4-addition reactions to form two PDA backbones, which constitute the two poles of the respective ladders. The bridging methylene chain length in the monomer was found to play a vital role as far as the polymerization process is concerned. Thus, the monomers with eight or four methylene units could form the ladder–PDAs by a two-step process, whereas the monomer containing two methylene units could only undergo one-step of 1,4-addition reaction. Further, it was found that the crystallinity of the polymers depends on the methylene chain length in the monomers, 4BCMU4A(8) being the most crystalline of all. These structural features strongly affect their absorption spectra. The third-order nonlinear optical susceptibilities (χ⁽³⁾) for these polymers were measured using third-harmonic generation method. The largest χ⁽³⁾ value obtained was 3.4 × 10⁻¹¹ esu for the poly[4BCMU4A(8)] thin film in resonant region. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3537–3548, 1999     

In situ measurement of the thermal expansion behavior of benzocyclobutene films

In situ measurement techniques suitable for determination of the coefficient of thermal expansion (CTE) in thin, spin‐cast polymer films in both the in‐plane and through‐plane directions are presented. An examination of the thermal expansion behavior of cyclotene thin films has been performed. In particular, the effect of film thickness on the in‐plane and through‐plane CTE and in‐plane Young's modulus of spin‐coated cyclotene films was examined. It is shown that the mechanical response of in situ cyclotene films can be adequately described by isotropic film properties. It was also demonstrated that there is no thickness dependence on the free‐standing mechanical properties or on the resulting through‐plane thermal strain in an in situ film. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 311–321, 1999