Surface free energy of ladderlike polyepoxysiloxane–diamine reaction systems

We studied three kinds of ladderlike polyepoxysiloxanes, which have different side groups grafted on the ladderlike backbones. 1,3‐Bis(aminopropyl)tetramethyl disiloxane (diamine) was used as the curing agent. The reaction between ladderlike polyepoxysiloxanes and diamine was investigated by contact angle measurements and surface free energy study. Several factors such as diamine amount, reaction time, and temperature can affect the systems' surface tension (or surface free energy), which were determined by two‐liquid geometric and three‐liquid acid‐base methods. The experimental results showed that an increase in the diamine amount in the reaction systems results in an increase in the polar part of surface free energy because of electron donate characteristics of the diamine. However, because epoxy (electron acceptor) and diamine (electron donor) react fast at elevated temperatures, increasing reaction temperature decreases the polar part of the surface free energy, while increases the nonpolar part of the surface free energy. The evolution of surface free energy with time for various epoxy–diamine reaction systems at various temperatures has also been studied. It was found that it took a relatively long time (50–60 h) to reach the equilibrium state. The experimental results can be well interpreted by the epoxy–diamine reaction mechanism and van Oss–Good's Lewis acid‐base theory. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1449–1460, 2000     

Study on thermal degradation mechanisms of comb polyacrylates containing long fluorocarbon side chains by TG/FTIR

Thermal degradation of two series of polyacrylates containing long fluorocarbon chains [abbr.: PF_nA {HCF₂(CF₂)_n−1  CH₂ O C(O) , n = 4, 6, 8, 10} and abbr.: PFF_nEA {CF₃(CF₂)_n−1  CH₂CH₂ O C(O) , n = 6, 8, 10}] was investigated by TG /FTIR. Thermal degradation behavior of polymers changed depending on the type of tie groups, which link the fluorocarbon chains to the main chain, and also on the length of fluorocarbon chains. It was clarified that the apparent activation energies (ΔE_a ) of PF_nA series obtained by Ozawa's method varied in the order of PF₄A > PF₆A > PF₈A > PF₁₀A, while those of PFF_nEA series having tie group of  CH₂ CH₂ O C(O) were almost constant. The results for PF_nA series (tie group:  CH₂ O C(O) ) are attributable to the shield effect of long fluorocarbon chains on the back‐biting reaction in the thermal degradation of comb polymers rather than the change of C C bond dissociation energy in the main chain. It was found that TG curves of PFF_nEA series were shifted to the lower temperature region than those of PF_nA. This result can be attributable to the scission of side groups followed by the evaporation of fluorocarbon compounds and carbon dioxide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2794–2803, 2000     

Sol–gel derived Si/C/O/N‐materials: molecular model compounds,xerogels and porous ceramics

Polymeric Si/C/O/N xerogels, with the idealized polymer network structure comprising [Si O Si(NCN)₃]_n moieties, were prepared by reactions of hexachlorodisiloxane (Cl₃Si O SiCl₃) with bis(trimethylsilyl)carbodiimide (Me₃Si NCN SiMe₃, BTSC). NMR and FTIR spectra indicate the existence of ‐NCN‐ and Si O Si‐ units in the xerogels and also in the ceramic materials obtained upon pyrolysis. The feasibility of this reaction protocol was confirmed on the molecular level by the deliberate synthesis of the macrocyclic compound [SiPh₂ O SiPh₂(NCN)]₂, the crystal structure and spectroscopic data of which are reported. The influence of pyridine as a catalyst for the cross‐linking reaction was studied. The degree of cross‐linking increased within the polymers with the addition of pyridine. It was shown by the reaction of hexachlorodisiloxane with excess pyridine that the latter appears to activate only one out of the two ‐SiCl₃ moieties under formation of hexacoordinated silicon compounds. The crystal structure of Cl₃Si O SiCl₃(pyridine)₂ is presented. Quantum chemical calculations are in support of this adduct being a potential intermediate in the pyridine catalyzed sol–gel process. The ceramic yield after pyrolysis of the Si/C/O/N‐xerogels at 1000 °C, which reaches values up to 50%, was found to depend on the aging protocol (time, temperature), whereas no correlation was found with the amount of pyridine added for xerogel synthesis. The Si/C/N/O‐ceramics obtained after pyrolysis at 1000 °C under NH₃ are completely amorphous. Chemically they have to be considered as hybrids between an ideal [SiOSi(NCN)₃]_n network and glass‐like Si₂N₂O. The products are mesoporous with closed pores and a broad pore size distribution. Copyright © 2011 John Wiley & Sons, Ltd.     

F3B · OEt2‐Promoted Intramolecular Si to C Phenyl Group Migration: A Highly Diastereoselective Synthesis of (4S,5S)‐4‐Hydroxy‐5‐phenyl‐2‐pyrrolidinone

A highly diastereoselective approach to N‐protected cis‐(4S,5S)‐4‐hydroxy‐5‐phenyl‐2‐pyrrolidinone is reported. The key step is a boron trifluoride etherate–promoted chemoselective intramolecular Si→C phenyl group migration.     

Synthesis,characterization, and thermal properties of ladderlike polyepoxysiloxanes

Starting from trichlorosilanes and using 1,4‐phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl‐co‐alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, ¹H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215–2222, 2001     

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     

UV Laser‐Induced Gas‐Phase Copolymerization of Carbon Disulfide and Ethene

Summary: The laser irradiation at 193 nm of a gaseous mixture of carbon disulfide and ethene induces the copolymerization of both compounds and affords the chemical vapour deposition of a C/S/H polymer, the composition of which indicates the reaction between two to three CS₂ molecules and one C₂H₄ molecule. Polymer structure is interpreted on the basis of X‐ray photoelectron and FT‐IR spectra as consisting of >CS, >CC<,  CH₂ CH₂ , (CC)S_nC_{4 − n},  C (CS) S ,  S (CS) S , and C S S C configurations. The gas‐phase copolymerization of carbon disulfide and ethene represents the first example of such a reaction between carbon disulfide and a common monomer.

Scheme showing the expected reaction of excited CS₂ molecules with other CS₂ molecules to form dimers, which then react with another CS₂ molecule or add to ethene.     

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     

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     

Facile synthesis of hyperbranched poly(p‐phenyleneethynylene‐alt‐m‐phenyleneethynylene) with narrow dispersity and high branching degree by sonogashira polymerization of an AB2 monomer

An AB₂ monomer PhBr₂  C  C  Ph  C  CH containing one acetylene group and two bromide groups was efficiently synthesized by a strategy based on the different reactivity between aromatic iodide and bromide in Sonogashira reaction. The Sonogashira polymerization of PhBr₂  C  C  Ph  C  CH was investigated to get hyperbranched poly(p‐phenyleneethynylene‐alt‐m‐phenyleneethynylene) (hb‐PMPE) in terms of the effects of monomer addition method, core molecule with different functionality, and ratio of [monomer]/[core molecule]. The results showed that narrow dispersities (D) (D: 1.23∼1.50) were obtained by slow monomer addition and with core molecule. Bifunctional core molecule induced narrower dispersity than monofunctional core molecule. The molecular weight of hb‐PMPE increased with increasing ratio of [monomer]/[core molecule], however, a negative deviation from calculated value was observed. The dispersity slightly increased with increasing [monomer]/[core molecule]. When the ratio of [monomer]/[core molecule] was below 50/1, monomodal distribution was observed; whereas when the ratio increased to 70/1, bimodal distribution was obtained. All the polymers showed degrees of branching (DBs) around 0.6. The hb‐PMPEs showed one major absorption band with λ_max around 330 nm, and emission band with λ_max around 390 nm. All the polymers showed relative quantum yields (Φ_r) above 0.5 in dilute THF solution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 96–104     

Amorphous silicon carbonitride thin‐film coatings produced by remote nitrogen microwave plasma chemical vapour deposition using organosilicon precursor

Amorphous silicon carbonitride (a‐SiCN) films were produced by remote nitrogen plasma chemical vapour deposition (RP‐CVD) from bis(dimethylamino)methylsilane precursor. The effect of substrate temperature (T _S) on the kinetics of RP‐CVD, chemical structure, surface morphology and some properties of the resulting films is reported. The T _S dependence of film growth rate implies that RP‐CVD is an adsorption‐controlled process. Fourier transform infrared spectroscopic examination revealed that an increase in T _S from 30 to 400°C involves the elimination of organic moieties from the film and the formation of Si─C and Si─N network structure. The films were characterized in terms of their surface roughness and basic physical and optical properties, such as density and refractive index, respectively. Reasonably good relationships between the structural parameters represented by relative integrated intensity of infrared absorption bands from the Si─C and Si─N bonds (controlled by T _S) and the film properties are determined. Due to their small surface roughness, high density and high refractive index, the a‐SiCN films produced at T _S ≥ 350°C would seem to be useful protective coatings for metals and optical devices.     

Synthesis and chiroptical properties of L‐valine‐containing poly(phenylacetylene)s with (a)chiral pendant terminal groups

Poly(phenylacetylene)s containing L ‐valine residues (P 1 ) with (a)chiral pendant terminal groups R^(*) [?(HC?C{C₆H₄CONHCH[CH(CH₃)₂]COO? R^(*)})_n?]; R^(*) = 1‐octyl (P 1 o), (1S,2R,5S)‐(+)‐menthyl [P 1 (+)], (1R,2S,5R)‐(?)‐menthyl [P 1 (?)] are designed and synthesized. The polymers are prepared by organorhodium catalysts in high yields (yield up to 88%) with high molecular weights (M_w up to ?6.4 × 10⁵). Their structures and properties are characterized by NMR, IR, TGA, UV, and circular dichroism analyses. All the polymers are thermally fairly stable (T_d ≥ 320 °C). The chiral moieties induce the poly(phenylacetylene) chains to helically rotate in a preferred direction. The chirality of the pendant terminal groups affects little the helicity of the polymers but their bulkiness stabilizes the helical conformation against solvent perturbation. The backbone conjugation and chain helicity of the polymers can be modulated continuously and reversibly by acid. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2117–2129, 2006     

Facile Soap‐Free Miniemulsion Polymerization of Methyl Methacrylate via Reverse Atom Transfer Radical Polymerization

A facile soap‐free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water‐soluble potassium persulfate (KPS) or 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (V‐50) both as the initiator and the stabilizer, and using an oil‐soluble N,N‐n‐butyldithiocarbamate copper (Cu(S₂CN(C₄H₉)₂)₂) as the catalyst without adding any additional ligand. Polymerization results demonstrated the “living”/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300–700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain‐extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive  S C(S) N(C₄H₉)₂ group in the chain end.     

Synthesis and properties of azobenzene‐containing poly(1‐alkyne)s with different functional pendant groups

1‐Alkynes containing azobenzene mesogenic moieties [HC?C(CH₂)₉? O? ph? N?N? ph? O? R; R = ethyl ( 1 ), octyl ( 2 ), decyl ( 3 ), (S)‐2‐methylbutyl ( 4 ), or (S)‐1‐ethoxy‐1‐oxopropan‐2‐yl ( 5 ); ph = 1,4‐phenyl] were synthesized and polymerized in the presence of a Rh catalyst {(nbd)Rh⁺[B(C₆H5)₄]^?; nbd = 2,5‐norbornadiene} to yield a series of liquid‐crystalline polymers in high yields (e.g., >75%). These polymers had moderate molecular weights (number‐average molecular weight ≥ 12,000), high cis contents in the main chain (up to 83%), good thermal stability, and good solubility in common organic solvents, such as tetrahydrofuran, chloroform, and dichloromethane. These polymers were thoroughly characterized by a combination of infrared, nuclear magnetic resonance, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy, and two‐dimensional wide‐angle X‐ray diffraction techniques. The liquid‐crystalline behavior of these polymers was dependent on the tail group attached to the azobenzene structure. Poly‐ 1 , which had the shortest tail group, that is, an ethyl group, showed a smectic A mesophase, whereas poly‐ 2 , poly‐ 3 , and poly‐ 5 , which had longer or chiral tail groups, formed smectic C mesophases, and poly‐ 4 , which had another chiral group attached to the azobenzene structure, showed a chiral smectic C mesophase in both the heating and cooling processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4532–4545, 2006     

Synthesis of triarylamine‐containing poly(arylene ether)s by nucleophilic aromatic substitution reaction

We report synthesis of a series of new triarylamine‐containing AB‐type monomers and their polymers via nucleophilic aromatic substitution (S_NAr) reaction. Monomers consisting of a hydroxyl group at the para position of the nitrogen group in one phenyl ring and a fluorine leaving group at the para position in another phenyl ring were synthesized via palladium‐catalyzed amination reaction. The fluorine leaving group was activated by trifluoromethyl group at the ortho position and an electron‐withdrawing group (EWG) introduced at the para position of the unsubstituted phenyl ring that enabled control over monomer reactivity. S_NAr reaction of the monomers successfully produced corresponding poly(arylene ether)s with pendant EWGs that exhibited good solubility and thermal stability. Optical and electrochemical properties of the polymers were also affected by incorporation of EWGs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2692‐2702     

Gel formation in cationic polymerization of divinyl ethers. II. 2,2-Bis{4-[(2-vinyloxy)ethoxy]phenyl}propane

Cationic polymerization of 2,2-bis{4-[(2-vinyloxy)ethoxy]phenyl}propane [CH₂CH O CH₂CH₂O C₆H₄ C(CH₃)₂ C₆H₄ OCH₂CH₂ O CHCH₂; 2], a divinyl ether with oxyethylene units adjacent to the polymerizable vinyl ether groups and a bulky central spacer, was investigated in CH₂Cl₂ at 0°C with the diphenyl phosphate [(C₆H₅O)₂P(O)OH]/zinc chloride (ZnCl₂) initiating system. The polymerization proceeded quantitatively and gave soluble polymers up to 85% monomer conversion. In the same fashion as the polymerization of 1,4-bis[2-vinyloxy(ethoxy)]benzene (CH₂CH O CH₂CH₂O C₆H₄ OCH₂CH₂ O CHCH₂; 1) that we already studied, the content of the unreacted pendant vinyl ether groups of the produced soluble polymers decreased with monomer conversion, and almost all the pendant vinyl ether groups were consumed in the soluble products prior to gelation. Alternatively, endo-type double bonds were gradually formed in the polymer main chains by chain transfer reactions and other side reactions as the polymerization proceeded. The polymerization behavior of isobutyl vinyl ether (3), a monofunctional vinyl ether, under the same conditions, showed that the endo-type olefins in the polymer backbones are of no polymerization ability with the growing active species involved in the present polymerization systems. These results indicate that the intermolecular crosslinking reactions occurred primarily by the pendant vinyl ether groups, and the final stage of crosslinking process leading to gelation also may occur by the small amount of the residual pendant vinyl ether groups (supposedly less than 2%). The formation of the soluble polymers that almost lack the unreacted pendant vinyl ether groups is most likely due to the frequent occurrence of intramolecular crosslinking reactions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1931–1941, 1999     

Synthesis and characterization of soluble,fluorescent poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s containing 1,3,5‐triphenylbenzene segments

The bisphenol 4,4″‐dihydroxy‐5′‐phenyl‐m‐terphenyl ( 4 ), containing a 1,3,5‐triphenylbenzene moiety, was synthesized from a pyrylium salt obtained by the reaction of benzaldehyde with p‐methoxyacetophenone with boron trifluoride etherate as a condensing agent. Polymers were obtained from 4 by a nucleophilic displacement reaction with various activated difluoro monomers and with K₂CO₃ as a base. A series of new poly(arylene ether)s ( 8a – 8f ) were obtained that contained phenyl‐substituted m‐terphenyl segments in the polymer chain. Polymers with inherent viscosities of 0.41–0.99 dL/g were obtained in yields greater than 96%. The polymers were soluble in a variety of organic solvents, including nonpolar solvents such as toluene. Clear, transparent, and flexible films cast from CHCl₃ showed high glass‐transition temperatures (T_g = 198–270 °C) and had excellent thermal stability, as shown by temperatures of 5% weight loss greater than 500 °C. 4 was converted via N,N‐dimethyl‐O‐thiocarbamate into the masked dithiol 4,4″‐bis(N,N′‐dimethyl‐S‐thiocarbamate)‐5′‐phenyl‐m‐terphenyl and was polymerized with activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃ as a base in diphenyl sulfone as a solvent. A series of new poly(arylene thioether)s ( 9a – 9e ) were obtained with T_g values similar to those of 8a – 8e . 9a – 9e were further oxidized into poly(arylene sulfone)s with T_g values 40–80 °C higher than those for 8a – 8e and 9a – 9e . These polymers also had good solubility in organic solvents. A sulfonic acid group was selectively introduced onto the pendent phenyl group of polymers 8a and 8f by reaction with chlorosulfonic acid. The polymers were soluble in dipolar aprotic solvents and formed films via casting from dimethylformamide. Polymers 8a – 8f , 11a , and 11f showed blue and red fluorescence under ultraviolet–visible light with emission maxima at 380–440 nm. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 496–510, 2002; DOI 10.1002/pola.10136     

Preparation of poly(alkylenebenzimidazole) by ruthenium complex catalyzed polycondensation of 3,3′‐diaminobenzidine with α,ω‐diols

The reactions of 3,3′‐diaminobenzidine with 1,12‐dodecanediol in 1 : 1–1:3 molar ratios in the presence of RuCl₂(PPh₃)₃ catalyst give poly(alkylenebenzimidazole), [ (CH₂)₁₁ O (CH₂)₁₁ Im / (CH₂)₁₀ Im ]_n (Im: 5,5′‐dibenzimidazole‐2,2′‐diyl) (I_a‐I_d) in 71–92% yields. The relative ratio between the [(CH₂)₁₁ O (CH₂)₁₁ Im ] unit (A) and the [‐ (CH₂)₁₀ Im ] unit (B) in the polymer chain varies depending on the ratio of the substrates used. The polymer I_a obtained from the 1 : 3 reaction contains these structural units in a 98 : 2 ratio. The polymers are soluble in polar solvents such as DMF (N,N‐dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N‐methyl‐2‐pyrrolidone) and have molecular weights M_n (M_w) of 4,200–4,800 (4,800–6,500) by GPC (polystyrene standard). The polymerization of the diol and 3,3′‐diaminobenzidine in higher molar ratios leads to partial cross‐linking of the resulting polymers I_e and I_f via condensation of imidazole NH group with CH₂OH group. Similar reactions of 3,3′‐diaminobenzidine with α,ω‐diols, HO(CH₂)_mOH (m = 4–10), in a 1 : 3 molar ratio give the polymers containing [ (CH₂)_m−1 O (CH₂) _m−1 Im ] and [ (CH₂) _m−2 Im ] units with partial cross‐linked structures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1383–1392, 1999     

Synthesis of Poly(arylene ether amine)s from a Monomer Containing an Electron‐Donating Amine Group in a Nucleophilic Aromatic Substitution Reaction

Summary: Poly(arylene ether amine)s were synthesized by a nucleophilic aromatic substitution polycondensation of bis[4‐fluoro‐3‐(trifluoromethyl)phenyl]amine with several bisphenols. Even though the monomer has an electron‐donating diphenylamine moiety, which normally deactivates a nucleophilic aromatic substitution (S_NAr) reaction, the polymerization proceeded by a S_NAr reaction to give high‐molecular‐weight polymers. The polymers show good solubility in common organic solvents and have T_gs in the range of 123 °C to 177 °C.

High‐molecular‐weight poly(arylene ether amine)s synthesized by a S_NAr reaction with the monomer containing an electron‐donating diphenylamine moiety.     

Ab Initio energetics of Si?O bond cleavage

A multilevel approach that combines high‐level ab initio quantum chemical methods applied to a molecular model of a single, strain‐free Si O Si bridge has been used to derive accurate energetics for Si O bond cleavage. The calculated Si O bond dissociation energy and the activation energy for water‐assisted Si O bond cleavage of 624 and 163 kJ mol⁻¹, respectively, are in excellent agreement with values derived recently from experimental data. In addition, the activation energy for H₂O‐assisted Si O bond cleavage is found virtually independent of the amount of water molecules in the vicinity of the reaction site. The estimated reaction energy for this process including zero‐point vibrational contribution is in the range of −5 to 19 kJ mol⁻¹. © 2017 Wiley Periodicals, Inc.