Preparation and properties of high molecular weight poly(1-germa-) or poly(1-sila-cis-pent-3-enes)

High molecular weight poly(1,1-dimethyl-1-germa-cis-pent-3-ene), poly(1,1-diphenyl-1-germa-cis-pent-3-ene), poly(1,1-dimethyl-1-sila-cis-pent-3-ene), and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) have been prepared. The thermal stability of these polymers is found to increase with their molecular weight.     

Bulk anionic ring opening polymerization of silacyclopent-3-enes

Summary Poly[1,1-diphenyl-1-sila-cis-pent-3-ene](I), poly[1,1-dimethyl-1-sila-cis-pent-3-ene](II), poly[1-methyl-1-phenyl-1-sila-cis-pent-3-ene](III), poly[1-methyl-sila-cis-pent-3-ene](IV), and poly[1-phenyl-1-sila-cis-pent-3-ene](V) were prepared by bulk anionic ring opening polymerization of the corresponding 1-silacyclopent-3-enes, at room temperature by use n-butyllithium or t-butyllithium and HMPA as co-catalysts. No solvent (THF or diethyl ether) was utilized.     

Stress-strain behavior and dynamic mechanical properties of poly(1,1-dimethyl-1-sila-cis-pent-3-ene), poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and of these polymers after crosslinking with sulfur

Mechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1-dimethyl-1-sila-cis-pent-3-ene) (I) and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (II). Tensile strength, elongation at break, modulus, bending modulus, T_g, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.     

Synthesis and characterization of poly(1-sila-cis-pent-3-enes) substituted with pendant pyridinyl groups

Poly[1-methyl-1-[3′-(3″-pyridinyl)propyl]-1-sila-cis-pent-3-ene], poly[1-phenyl-1-[3′-(3″-pyridinyl)propyl)-1-sila-cis-pent-3-ene], and poly[1-phenyl-1-(4′-pyridinyl)-1-sila-cis-pent-3-ene] were synthesized by the anionic ring-opening polymerization of 1-methyl-1-[3′-(3″-pyridinyl)propyl]-1-silacyclopent-3-ene, 1-phenyl-1-[3′-(3″-pyridinyl)propyl]-1-silacyclopent-3-ene, and 1-phenyl-1-(4′-pyridinyl)-1-silacyclopent-3-ene, respectively. These are the first polycarbosilanes which contain heterocyclic pyridine units as side-chain substituents. These polymers were characterized by¹H,¹³C, and²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distributions were determined by gel permeation chromatography, glass transition temperatures, by differential seanning calorimetry: (DSC) and thermal behavior, by thermogravimetric analysis. (TGA).     

Partial and complete hydrogenation of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene)

Summary Poly(1-methyl-1-phenyl-1-silapentane)(II), andblock copoly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene/1-methyl-1-phenyl-1-silapentane) (block-III) have been prepared by catalytic hydrogenation of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene)(I) over 5% palladium on carbon. These polymers have been characterized by¹H,¹³C and²⁹Si NMR as well as IR spectroscopy. Molecular weight distributions have been evaluated by gel permeation chromatography (GPC). Thermal stabilities have been measured by thermogravimetric analysis (TGA). Glass transition temperatures (T_g's) have been determined by differential scanning calorimetry (DSC).     

Synthesis of poly(1-methyl-1-phenyl-1-silapentane) by chemical reduction of poly)1-methyl-1-phenyl-1-sila-cis-pent-3-ene with diimide

Summary Poly(1-methyl-1-phenyl-1-silapentane) (I) has been prepared by the chemical reduction of the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene (cis-II) with diimide, which was generatedin-situ by the thermal decomposition ofp-toluenesulfonhydrazide in refluxing toluene. At lower temperature (100°C),cis-II is isomerized byp-toluenesulfinic acid to lower molecular weight poly(1-methyl-1-phenyl-1-sila-cis andtrans-pent-3-ene) (cis/trans-II). Protodesilation of I with trifluoromethanesulfonic acid yields poly(1-methyl-1-trifluoromethanesulfonyl-1-silapentane) (III). The structures of I andcis/trans-II have been characterized by¹H,¹³C and²⁹Si NMR, GPC, TGA and elemental analysis. The structure of I has been characterized spectroscopically by¹H,¹³C,¹⁹F and²⁹Si NMR.     

Synthesis and microstructure of poly(1-phenyl-1-sila-cis-pent-3-ene)

Summary poly(1-Phenyl-1-sila-cis-pent-3-ene) (I) has been prepared by the anionic ring opening polymerization of 1-phenyl-1-sila-cyclopent-3-ene (II). This reaction is co-catalyzed by n-butyl-lithium and HMPA in THF at low temperature. I has been characterized by ¹H, ¹³C and ²⁹Si NMR, IR, UV, GPC and TGA. The low molecular weight of l permits end group analysis. Pyrolysis of l gives significant char yields.     

Ring opening metathesis polymerization of 1,1-diphenyl-1-sila-cyclopent-3-ene

Summary 1,1-Diphenyl-1-silacyclopent-3-ene (I) has been polymerized by ring opening metathesis using tungsten hexachloride and either cyclopentene or cyclohexene as an initiator, with or without tetraphenyltin as a cocatalyst. The product polymer poly(1,1-diphenyl-1-sila-cis-pent-3-ene) (II) has been characterized by¹H,¹³C, and²⁹Si NMR and IR spectroscopy.     

Synthesis and characterization of poly(1-sila-cis-pent-3-enes) substituted with pendant pyridinyl groups

Poly[1-methyl-1-[3-(3-pyridinyl)propyl]-1-sila-cis-pent-3-ene], poly[1-phenyl-1-[3-(3-pyridinyl)propyl)-1-sila-cis-pent-3-ene], and poly[1-phenyl-1-(4-pyridinyl)-1-sila-cis-pent-3-ene] were synthesized by the anionic ring-opening polymerization of 1-methyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, 1-phenyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, and 1-phenyl-1-(4-pyridinyl)-1-silacyclopent-3-ene, respectively. These are the first polycarbosilanes which contain heterocyclic pyridine units as side-chain substituents. These polymers were characterized by¹H,¹³C, and²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distributions were determined by gel permeation chromatography, glass transition temperatures, by differential seanning calorimetry: (DSC) and thermal behavior, by thermogravimetric analysis. (TGA).     

Anionic ring opening polymerization of 1-silacyclopent-3-ene

Summary 1-Silacyclopent-3-ene (I) undergoes anionic ring opening polymerization catalyzed by methyllithium/HMPA to yield poly(1-sila-cis-pent-3-ene) (II). II was characterized by ¹H, ¹³C, and ²⁹Si NMR, GPC, TGA and elemental analysis. The low molecular weight of II permits end group analysis. Pyrolysis of II gives high char yields. These have been characterized by EDS.     

Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene)(Cl2C-I): synthesis and characterization of poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) CH2-I)

Summary Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (Cl₂C-I) yields poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) (CH₂-I) which has been characterized by ¹H, ¹³C and ²⁹Si NMR spectroscopy as well as by elemental analysis. The molecular weight distribution of CH₂-I has been determined by GPC and its thermal stability by TGA. Its glass transition temperature was obtained by DSC.     

Anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene

Summary Poly(1-phenyl-1-vinyl-1-sila-cis-pent-3-ene) (I) has been prepared by the anionic ring opening polymerization of 1-phenyl-1-vinyl-1-silacyclopent-3-ene (II) co-catalyzed by n-butyllithium and hexamethylphosphoramide (HMPA) in THF at-78°C. I has been characterized by ¹H, ¹³C and ²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distribution of I has been determined by gel permeation chromatography (GPC), its thermal stability by thermogravimetric analysis (TGA) and its glass transition temperature (T_g) by differential scanning calorimetry (DSC). Thermal degradation of I in an inert atmosphere gives a twenty-seven percent char yield.     

Anionic ring opening polymerization of 3,4-benzo-1,1-dimethyl-1-silacyclopentene

Summary Treatment of 3,4-benzo-1,1-dimethyl-1-silacyclopentene with a catalytic amount of n-butyllithium and HMPA in THF yields poly(3,4-benzo-1,1-dimethyl-1-silapentene). This polymer has the highest melting temperature, glass transition temperature and thermal stability of any poly (1-silapent-3-ene) yet prepared.     

Study on unsaturated structures of polyhexene,poly(4-methylpentene) and poly(3-methylpentene) prepared with metallocene catalysts

Hex-1-ene (hexene), 4-methylpent-1-ene (4-MP-1) and 3-methylpent-1-ene (3-MP-1), homopolymerizations were conducted by using metallocenes, En(Ind)₂ZrCl₂ and iPr(Cp)(Flu)ZrCl₂, with methylaluminoxane. ¹H NMR analyses of the resulting polymers were carried out to identify the unsaturated structures of these polymers. In polyhexene and poly(4-MP-1), the detected main unsaturated structure was di-substituted vinylene. On the other hand, in poly(3-MP-1), vinylidene and tri-substituted vinylene structures were mainly observed for the first time.     

Nuclear spin—lattice relaxation and molecular motions in isotactic poly(but-1-ene) and (but-1-ene)—propylene copolymers in solution

¹³C spin—lattice relaxation times have been measured at 25.15 MHz on poly(but-1-ene) and (but-1-ene)—propylene copolymers, as a function of molecular weight and concentration in 1,2,4-trichlorobenzene, and over the 50°–150°C temperature range. Maximum nuclear Overhauser enhancement was observed for all carbons. Independence of T₁ from molecular weight and bulk sample viscosity for solutions less concentrated than 50% w/v, indicates that relaxation is dominated by local conformational rearrangements rather than by overall tumbling of the macromolecule. Relaxation studies on copolymers show that this segmental motion affects only short sequences of the chain. No influence of stereochemical configurations is observed. Relaxation data for backbone carbons was interpreted in terms of a single τ isotropic motional model. Internal rotations of side CH₂ and CH₃ groups were analysed using the two and three correlation times Woessner models, and show little dependence on an eventual anisotropy of chain motion. Similar temperature dependence (18–21 kJ/mol) is observed for chain and side carbons, and even if internal reorientation of side CH₃ groups is much more rapid, it appears interlinked with segmental motion.     

Degradation and geometric isomerization of poly(N-propargylamides)

The stability of several poly(N-propargylamides) was investigated in solution and in solid state on the basis of molecular weight change with time, and further their thermal stability was investigated by TGA. When the stability of poly(N-propargylamides) with varying pendent groups was compared, polymers with pendent groups of moderate size showed the highest stability in solution. Too short and too bulky pendent groups were not favorable for the stability of polymers. When poly(N-propargylheptanamide) (poly(6)) was stored in THF as solution at −20 °C in the absence of oxygen in dark, its degradation rate was the lowest. The degradation rate of poly(6) depended on the solvents used, which may be related to different solubility of oxygen in these solvents. Polymers with high cis contents degraded faster than polymers with low cis contents did. Addition of TEMPO and DPPH into the poly(6)/THF solution more or less depressed the degradation of poly(6). The degradation of polymer main chain in solution was always accompanied by the decrease of cis content, i.e. geometric isomerization from cis- to trans-structure. When the polymers were stored in the solid state at −20 °C, the polymers having alkyl pendent groups with moderate length were more stable than those with bulky pendent groups. Geometric isomerization occurred along with degradation in the solid state as well.     

Synthesis and characterization of poly(1-methyl-1-silabutane), poly(1-phenyl-1-silabutane) and poly(1-silabutane)

Summary Anionic ring opening polymerization of 1-methyl-1-silacyclobutane, 1-phenyl-1-silacyclobutane and 1-silacyclobutane co-catalyzed by n-butyllithium and hexamethylphosphoramide (HMPA) in THF at-78°C yields poly(1-methyl-1-silabutane), poly(1-phenyl-1-silabutane) and poly(1-silabutane) respectively. These saturated carbosilane polymers possess reactive Si-H bonds. They have been characterized by ¹H, ¹³C and ²⁹Si NMR as well as FT-IR and UV spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography (GPC), thermal stabilities by thermogravimetric analysis (TGA) and glass transition temperatures (T_g) by differential scanning calorimetry (DSC).     

Synthesis and characterization of hyperbranched aromatic poly(ester-imide)s

The synthesis and characterization of hyperbranched aromatic poly(ester-imide)s are described. A variety of AB₂ monomers, N-[3- or 4-bis(4-acetoxyphenyl)toluoyl]-4-carboxyl-phthalimide and N-{3- or 4-[1,1-bis(4-acetooxyphenyl)]ethylphenyl}-4-carboxy phthalimides were prepared starting from condensation of nitrobenzaldehydes or nitroacetophenones with phenol and used for synthesis of hyperbranched poly(ester-imide)s containing terminal acetyl groups by transesterification reaction. These hyperbranched poly(ester-imide)s were produced with weight-average molecular weight of up to 6.87 g/mol. Analysis of ¹H NMR and ¹³C NMR spectroscopy revealed the structure of the four hyperbranched poly(ester-imide)s. These hyperbranched poly(ester-imide)s exhibited excellent solubility in a variety of solvents such as N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran and showed glass-transition temperatures between 217 and 255 °C. The thermogravimetric analytic measurement revealed the decomposition temperature at 10% weight-loss temperature (T_d¹⁰) ranging from 365 to 416 °C in nitrogen.     

Synthesis of thermosetting poly(phenylene ether) containing allyl groups

New thermosetting poly(2-allyl-6-methylphenol-co-2,6-dimethylphenol)s (3) have been developed by oxidative coupling copolymerization of 2-allyl-6-methylphenol (1) with 2,6-dimethylphenol (2), followed by thermal curing. Copolymerization was conducted in nitrobenzene in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen, producing high molecular weight copolymers (M_n∼50,000) with broad molecular weight distributions (M_w/M_n∼35). The structure of resulting copolymers 3 was characterized by IR, ¹H, and ¹³C NMR spectroscopy. Cross-linking reactions of copolymers were carried out by thermal treatment in the absence or presence of a peroxide (3 wt%, 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-butane). The 10% weight loss and glass transition temperatures of the cured copolymers were 436 °C in nitrogen and 235 °C, respectively after curing at 70 °C for 1 h and 300 °C for 1 h. The average refractive index of the cured copolymer (3b) film was 1.5407, from which the dielectric constant (ε) at 1 MHz was estimated as 2.6. The ε and dissipation factor of copolymer-films at 1 MHz were directly measured from their capacitances as 2.5-2.6 and 0.0015-0.0019, respectively.     

Synthesis and characterization of poly([3,4,c]furano-1-germa-1,1-dimethylcyclopentane)

Summary Poly([3,4,c]furano-1-germa-1,1-dimethylcyclopentane) (I) has been prepared by the anionic ring opening polymerization of 3-oxa-7,7-dimethyl-7-germabicyclo[3.3.0]- octa-1,4-diene (II) co-catalyzed byn-butyllithium and HMPA in THF. I has been characterized by¹H,¹³C NMR, IR and UV spectroscopy as well as by elemental analysis. The molecular weight distribution of I has been determined by gel permeation chromatography (GPC), its thermal stability established by thermogravimetric analysis (TGA) and its glass transition temperature (T_g) measured by differential scanning calorimetry (DSC).