Stepwise Coupling Polymerization Research Articles

Structural studies on ladder phenylsilsesquioxane oligomers formed by polycondensation of cyclotetrasiloxanetetraols

Poly(phenylsilsesquioxanes) of regular ladder like structure were synthesized by condensation of [PhSi(O)OH]4 obtained in situ from sodium cyclosiloxanolate {(Na+)4[PhSi(O)O−]4} nL (L = iPrOH, H2O). The composition of oligomers present in the reaction mixture was analysed with MALDI ToF during the course of polycondensation. Redistribution of siloxane bonds and cyclization of macromolecules were detected. Cyclic LPSQ-Ph species and silsesquioxane redistribution in basic medium was also observed for oligo(phenylsilsesquioxanes) obtained by stepwise coupling polymerization. TGA and FTIR analysis of thermal decomposition process indicated significant differences in the course of structural rearrangements at high temperatures for both types of polysilsesquioxanes.

Promising Functional Materials Based on Ladder Polysiloxanes

AbstractPreparation of real ladder polysiloxanes (LPSs), including both oxygen‐bridged ladder polysilsesquioxanes (LPSQs) and organo‐bridged ladder polysiloxanes (OLPSs), had been a great challenge to polymer chemists from 1960 until the successful synthesis of LPSs via the supramolecular architecture‐directed stepwise coupling polymerization (SCP) in the early 1980s. This opened up a new field of LPS‐based advanced materials. As key building blocks, LPSs are used to construct a variety of polysiloxanes with special steric configurations and functions, such as mesomorphic LPSs, tubular polysiloxanes (TPs), and pseudo‐sieve‐plate polysiloxanes (pseudo‐SPSs). With excellent temperature and radiation resistance, good solubility, and fine optical and mechanical properties, all these polysiloxanes demonstrate very promising prospects in the advanced materials realm. Here, the synthesis of well‐ordered LPSs is presented and features of fishbone‐like and rowboat‐like liquid crystalline polysiloxanes are discussed. Special emphasis is given to typical applications of LPSs, TPSs, and pseudo‐SPSs in the areas of liquid crystal displays, microelectronics packaging, and nonlinear optical materials.

Copolymerization Studies of Urethane Methacrylate and Ladder-Like Polysilsesquioxane Containing Side Chain Methacrylate Groups

Urethane methacrylate (UMA) prepolymer was prepared by reacting 2 mole tolylene diisocyanate with 1 mole polyethylene glycol (molecular weight 400) followed by end-capping with 2 mole 2-hydroxyethyl methacrylate in N, N-dimethylformamide (DMF) solvent using stannous octoate as a catalyst. It took 72 h for complete reaction at ambient temperature as determined by monitoring the isocyanate peak at 2269 cm-1. Ladder-like polysilsesquioxane (LPS) containing side chain methacrylate groups was prepared by stepwise coupling polymerization. Different weight fractions of UMA and LPS in DMF were copolymerized using 1% (w/w) dibenzoyl peroxide at 80°C for 24 h followed by post curing at 100°C for 4-5 h in a nitrogen atmosphere. The copolymers were characterized by Fourier transform infrared analysis, solid-state 13C NMR spectroscopy, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis. No glass transition temperatures were observed for the copolymers by DSC. The WAXD patterns of copolymers showed a broad peak corresponding to the width of double chain of LPS, indicating the incorporation of LPS in copolymers. These copolymers were more resistant to acid medium. The temperature of 5% weight loss increased with increasing silsesquioxane content in both air and nitrogen atmospheres, and verified the incorporation of LPS in the copolymers.

Investigation of thermal crosslinking and pyrolysis of ladderlike silsesquioxanes in vacuum by XRD measurements and weight analysis

In this paper, we first synthesized ladderlike poly(vinylsilsesquioxane) (LPVS) by stepwise coupling polymerization on the basis of amido H-bonding self-assembling template from vinyltrichlorosilane (VTCS) monomers. We made the substitutional vinyl of LPVS polymerized at one same side (LPVS-SP), then put it in the vacuum conditions and let it carbonized at 500, 600, 700, 800 and 900 °C, respectively to observe its thermal behavior. In our experiment, 700 °C can be regarded as a distinct turning point of temperature from weight loss to inter-molecules thermal crosslinking, which can be observed by X-ray diffraction (XRD) measurements and Thermogravimetric analysis (TGA). At the same time, SEM and TEM photos of the carbonization products give very rigidity topography at micron scale, which are the auxiliary evidence for our conclusion. We also present one reasonable thermal carbonization and crosslinking mechanism of LPVS-SP at high temperature in vacuum by remaining products weight analysis.

Curing Studies of Ladder-Like Poly(allylsilsesquioxane) and its copolymers by Differential Scanning Calorimetry

Using stepwise coupling polymerization method, three ladder-like poly(allylsilsesquioxane)s have been synthesized. The prepared ladder-like polymers contain (i) allyl, (ii) allyl and methyl and (iii) allyl and phenyl as side chain groups. They were characterized by FTIR, NMR, WAXD, DSC and TGA. Characterization indicated that they had ladder-like structure. All the polymers were cured by 2,2’-dibenzoyl peroxide (1% W/W) and the kinetics for the bulk polymerization of these polysilsesquioxanes was followed by dynamic DSC. The Ozawa and Kissinger methods were used to calculate activation energies for curing of these polysilisesquioxanes. Cured samples were characterized by FTIR, DSC and TGA.

Synthesis and characterization of ethoxy‐terminated ladder‐like polymethylsilsesquioxane oligomer

AbstractA fully ethoxy‐terminated ladder‐like polymethylsilsesquioxane oligomer (EtO‐Me‐T) has been synthesized and characterized for the first time using an effective transient catalyst (tetramethylammonium hydroxide, TMAH) via the dehydration alcoholysis reaction of hydroxy‐terminated ladder‐like polymethylsilsesquioxane (HO‐Me‐T) prepared by a modified stepwise coupling polymerization approach. Compared with the common acidic or basic catalysts, use of the transient catalyst TMAH can not only make the HO‐Me‐T molecules fully ethoxy‐terminated but also enables the catalyst to be readily and thoroughly removed after completion of the alcoholysis reaction. It is noteworthy that the common acidic or basic catalysts widely used in the dehydration alcoholysis reaction are clearly unsuitable for the preparation of EtO‐Me‐T oligomer because the latter would be hydrolyzed unavoidably back to the parent HO‐Me‐T during the washing process. In addition, preliminary exploration indicates that, when compared with the tetraethyl orthosilicate (Si(OEt)4) generally used as a crosslinking agent for the room‐temperature vulcanization of silicone rubber (RTV‐SR), the oligomer EtO‐Me‐T is a promising replacement which can greatly improve the mechanical properties of RTV‐SR Copyright © 2003 Society of Chemical Industry

H-bonding assisted template synthesis of a novel ladder-like organo-bridged polymethylsiloxane

A novel soluble aryl amide-bridged ladder-like polymethylsiloxane (ALPS) was synthesized via a stepwise coupling polymerization by means of H-bonding self-assembling template. The new monomer N, N′-di(4-methyldiethoxysiloxyl-phenyl)-terephthaloyl amide, prepared by dehydrocoupling reaction of N, N′-di(4-hydroxy-phenyl)-terephthaloyl amide with methyldiethoxysilane, was hydrolyzed in a dilute solution at low temperature to form a proposed ladder-like supramolecular intermediate through amido H-bonding interaction, which was further condensed to form polymer ALPS using dibuthyltindilaurate as catalyst. A combination of techniques including 1H NMR, 29Si NMR, FTIR, X-ray diffraction (XRD), DSC, and light scattering were used to characterize the titled polymer ALPS. The results indicate the polymer ALPS possesses an ordered ladder-like architecture.

Synthesis, Characterization, and Polymerization Kinetics of Novel Ladder‐Like Polysilsesquioxanes Containing Side‐Chain Propyl Methacrylate Groups

AbstractThree ladder‐like polysilsesquioxanes containing side‐chain propyl methacrylate groups have been synthesized successfully by stepwise coupling polymerization. The prepared ladder‐like polymers are polysilsesquioxanes containing 100 mol‐% propyl methacrylate side groups and two copolymers containing 70 mol‐% methyl or phenyl groups and 30 mol‐% propyl methacrylate side groups. They were characterized by FT‐IR, 1H NMR, proton‐decoupled 13C NMR, and 29Si NMR spectroscopies, gel‐permeation chromatography (GPC), wide‐angle X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and thermo‐gravimetric analysis (TGA). Characterization data indicate that these polymers have ordered ladder‐like structures with possible defects. At appropriate conditions, crystals of homopolymer were grown and are in the shape of a parallelogram. All three polymers were cured by 2,2′‐azoisobutyronitrile (1% w/w) and the kinetics for the bulk polymerization of these polysilsesquioxanes was followed by dynamic DSC method. Ozawa and Kissinger methods were used to calculate the activation energy for curing. Both the frequency factor and the activation energy of the homopolymer were found to be higher than the copolymers. Cured samples had a higher thermal stability than uncured samples. Chemical structure of LPS.imageChemical structure of LPS.

Hydrogen‐bonding‐aided synthesis of novel ladderlike organobridged polysiloxane containing side‐chain naphthyl groups

AbstractWith a hydrogen‐bonding template, a novel soluble aryl amide‐bridged ladderlike polysiloxane, containing naphthyl as the side‐chain group, has been successfully synthesized via a stepwise coupling polymerization. It is proposed that the monomer, N,N′‐di(3‐naphthyldiethoxylsilyl‐propyl)‐[4,4′‐oxybis(benzyl amide)], prepared by Grignard and hydrosilylation reactions, undergoes self‐assembly first via amido hydrogen bonding and then via hydrolysis, followed by condensation under controlled reaction conditions to yield a high molecular weight, soluble, dark yellow polymer. The analytical results (Fourier transform infrared, 1H NMR, 29Si NMR, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry) show that the polymer possesses an ordered ladderlike architecture. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 636–644, 2003

Hydrogen-Bonding-Directed Template Synthesis of Novel Stereo-Regular Organo-Bridged Ladder-Like Polymethylsiloxane

A novel stereo-regular organo-bridged ladder-like polymethylsiloxane (LPMS) was synthesized by a stepwise coupling polymerization on the basis of an amido H-bonding-assisted self-assembling template. The monomer N,N′-bis{4-[3-(diethoxymethylsilyl)propoxy]-phenyl}terephthalamide (M), prepared by hydrosilylation reaction at high temperature, was hydrolyzed in a dilute solution at a low temperature to form a ladder-like supramolecular intermediate through amido H-bonding interactions, which was further condensed to form the polymer LPMS. A combination of techniques including 1H NMR, 29Si NMR, and FT-IR spectroscopies X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to characterize the titled polymer LPMS, and the results indicate that the polymer possesses an ordered ladder-like structure. 29Si NMR spectrum of the polymer LPMS.

Studies on the Synthesis and Conductivity of a Novel Reactive Ladder‐Like Poly(β‐cyanoethylsilsesquioxane) and Poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)

AbstractTwo novel reactive poly(β‐cyanoethylsilsesquioxane) (CN‐T) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] (CN‐Me‐T) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, 1H NMR, 29Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10−6 S · cm−1 at room temperature and obviously increased with the raise of temperature. magnified image

A novel aryl amide-bridged ladderlike polymethylsiloxane synthesized by an amido H-bonding self-assembled template.

A novel soluble aryl amide-bridged ladderlike polymethylsiloxane (A-LPMS) was synthesized by stepwise coupling polymerization on the basis of amido H-bonding self-assembling template from monomer N,N'-bis(3-methyldiethoxylsilylpropyl)-[4,4'-oxybis(benzyl amide)]. The monomer was prepared in a high yield by the hydrosilylation reaction of template agent N,N'-diallyl-[4,4'-oxybis(benzyl amide)] with methyldiethoxysilane in the presence of dicyclopentadienylplatinum dichloride (Cp(2)PtCl(2)) as catalyst. A variety of techniques including (1)H NMR, (13)C NMR, (29)Si NMR, FTIR, XRD, DSC, and, especially, static and dynamic light scattering and viscosimetry were combined to confirm the presence of the ordered ladderlike structure of polymer A-LPMS.

Self‐assembling directed synthesis of a novel terephthalamide‐bridged ladderlike polysiloxane

AbstractA novel, soluble terephthalamide‐bridged ladderlike polysiloxane (L) was synthesized successfully for the first time by stepwise coupling polymerization. The process involved the hydrogen‐bonding self‐assembly of amido groups, which resulted in the formation of a more highly ordered polymeric structure. A novel monomer, bis(3‐methyldimethoxysilylpropyl) terephthalamide (M), was prepared by a hydrosilylation reaction in the presence of dicyclopentadienyl platinum dichloride as a catalyst. The structures of the monomer (M) and the polymer (L) were characterized by Fourier transform infrared, 1H NMR, 13C NMR, 29Si NMR, mass spectrometry, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry. All the characterization data indicated that the synthesized polymer (L) possessed an ordered ladderlike structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3161–3170, 2002

Novel microencapsulated curing accelerator for prolonging shelf life of epoxy resin composition

AbstractA novel micron‐sized microencapsulated curing accelerator, imidazole (Im), particles, was first prepared by an ultrasound‐assisted dispersing and spray‐drying method and can significantly prolong the shelf life of epoxy resin‐based microelectronic packaging material. The shell of the encapsulated particles was made from ladderlike copoly(phenyloctyl silsesquioxane) (Ph‐Oct‐T), which was synthesized by a “stepwise coupling polymerization” method. Its softening or flowing temperature can be adjusted by changing the composition. Carbon tetrachloride (CCl4) was chosen as both a solvent of the capsular material Ph‐Oct‐T and a suspending/precipitating agent of the fine Im particles. Subsequently, the solution containing Ph‐Oct‐T and suspended Im particles was treated by a spray‐drying process to produce the microencapsulated curing accelerator, Im particles, whose size and appearance was observed by scanning electronic microscopy (SEM). A greatly improved shelf life of the epoxy resin composition containing this microencapsulated curing accelerator was exhibited by curing tests and DSC measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 873–878, 2002

Synthesis and characterization of a novel polyorganosiloxane having a bigger sized tubular structure and its supramolecular clathrate

AbstractA novel polyorganosiloxane having a bigger sized tubular structure, tubular polymer (TP) was synthesized successfully by hydrosilylation reaction of reactive cis‐isotactic ladder‐like polyallylsilsesquioxane (Allyl‐T) with coupling agent p‐bis(dimethylhydrogensilyl)oxydiphenylene (M) in the presence of dicyclopentadienylplatinum(II) chloride (Cp2PtCl2) catalyst. A novel supramolecular TP clathrate (TP/LC) was prepared by in situ encapsulating rod‐like liquid crystalline molecule within the pore of TP. The Allyl‐T was prepared by stepwise coupling polymerization. Various characterization methods including solubility test, FT‐IR, 1H‐NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), vapour pressure osmometer (VPO), X‐ray diffraction (XRD), atomic force microscopy (AFM), polarized optical microscopy (POM) and molecular simulation were used and the results not only proved the existence of nano‐scale tubular structures in the TP, but also demonstrated that a novel soluble supramolecular clathrate had been formed. Copyright © 2002 John Wiley & Sons, Ltd.

Synthesis and characterization of polyorganosiloxane (POS) containing nano‐scale tubular structure and its supramolecular clathrate

AbstractA new polyorganosiloxane (POS) was synthesized successfully according to two plus two (2 + 2) mode by hydrosilylation reaction of reactive cis‐isotactic ladder‐like polyallylsilsesquioxane (Allyl‐T) with coupling agent 1,1,3,3‐tetramethyldisiloxane (H‐MM) using dicyclopentadienyl‐dichloroplatinium (Cp2PtCl2) as catalyst. Moreover, a novel supramolecular POS clathrate (POS/C) was formed by in situ encapsulating rod‐like liquid crystal molecule within the pore of POS. The Allyl‐T was prepared by stepwise coupling polymerization. A variety of characterization methods including solubility test, FT‐IR, 1H − NMR, differential scanning calorimetry (DSC) gel permeation chromatography (GPC), vapor pressure osmometry (VPO), X‐ray diffraction (XRD), atomic force microscopy (AFM), polarized optical microscopy (POM) and molecular simulation not only indicates nano‐scale tubular structures exist in the POS though some defective structures still exist, but also proves that novel soluble supramolecular clathrate has been formed. Copyright © 2001 John Wiley & Sons, Ltd.

Preparation of a new ladderlike oligosilsesquioxane with lateral aryl ester group

A new soluble ladder-like polysilsesquioxane with polar lateral aryl ester group, which has good adhesion properties and could be potential precursors of advanced functional materials such as catalyst carriers, polymeric solid electrolytes and microelectronic packaging materials etc., was successfully synthesized by stepwise coupling polymerization (SCP) method. The monomer used, methyl 4-trichlorosilylpropoxybenzoate, was synthesized by hydrosilylation reaction catalyzed by dicyclopentadienylplatinum(II) dichloride (Cp 2PtCl 2). The titled polymer was characterized by 1H NMR, 29Si NMR, FTIR, X-ray diffraction (XRD) and gel permeation chromatography (GPC). The characterization data demonstrate that the polymer possesses a typical ladder-like structure.

Synthesis and characterization of a novel soluble reactive ladder‐like polysilsesquioxane with side‐chain 2‐(4‐chloromethyl phenyl) ethyl groups

AbstractA new kind of soluble structure‐ordered ladder‐like polysilsesquioxane with reactive side‐chain 2‐(4‐chloromethyl phenyl) ethyl groups (L) was first synthesized by stepwise coupling polymerization. The monomer, 2‐(4‐chloromethyl phenyl) ethyltrichlorosilane (M), was synthesized successfully by hydrosilylation reaction with dicyclopentadienylplatinum(II) chloride (Cp2PtCl2) ­catalyst. Monomer and polymer structures were characterized by FT‐IR, 1H‐NMR, 13C‐NMR, 29Si‐NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vapor pressure osmometry (VPO) and X‐ray diffraction (XRD). This novel reactive ladder‐like polymer has promise potential applications as initiator for atom transfer radical polymerization, and as precursor for a variety of advanced functional polymers. Copyright © 2001 John Wiley & Sons, Ltd.

Study of the Steric Tacticity of Novel Soluble Ladderlike Poly(phenylsilsesquioxane) Prepared by Stepwise Coupling Polymerization

A novel kind of soluble ladderlike poly(phenylsilsesquioxane) (LPPS) was prepared by stepwise coupling polymerization. Various techniques, such as fluorescence spectroscopy, X-ray diffraction (XRD), molecular simulation and calculation, were combined to indicate that the steric structure in LPPS was predominantly cis-isotactic. It is anticipated that stepwise coupling polymerization is a useful synthetic method for preparing ladder-like poly(silsesquioxane)s with cis-isotactic structure, which have potential applications as functional polymers or as precursors for the further synthesis of novel advanced polymers. Schematic presentation of the steric strocture of LPPS: (a) cis-isotactic (b) cis-syndiotactic.

Synthesis and Characterization of Novel Alcohol-Soluble Ladderlike Poly(silsesquioxane)s Containing Side-Chain Hydroxy Groups

Two novel kinds of alcohol-soluble ladderlike poly(silsesquioxane)s containing side-chain hydroxy groups (OH-T1 and OH-T2) were prepared successfully for the first time by hydrolysis of ladderlike poly(silsesquioxane)s with side-chain ester groups (Ester-T1 and Ester-T2), which were synthesized by stepwise coupling polymerization. A variety of characterization methods including FT-IR, 1H NMR, 13C NMR, 29Si NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vapor pressure osmometry (VPO), gel permeation chromatography (GPC), and X-ray diffraction (XRD) were combined to demonstrate that the obtained alcohol-soluble polymers have ladderlike structures, although some structural defects still existed.