Living cationic polymerization route to poly(oligooxyethylene carbonate) vinyl ethers

The addition of dialkyl (R = Me or Et) carbonates to poly(oxyethylene)-based solid polymeric electrolytes resulted in enhanced ionic conductivities. Relatively high conductivities in lithium batteries with solutions of lithium salts in di(oligooxyethylene) carbonates such as R( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR (R = Et, n = 1, 2, or 3, m = 0, 1, 2, or 3) and related carbonates were obtained. In this respect, related comb-shaped poly(oligooxyethylene carbonate) vinyl ethers of the type  CH₂CH(OR) were prepared [R = ( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR′; (1) n = 2 or 3, m = 0, R′ = Et; (2) n = 2 or 3; m = 3, R′ = Me]. The direct preparation of derived target polymers of this class by polymerization of the corresponding vinyl ether-type monomers could not be achieved because of a rapid in situ decarboxylative decomposition of these monomers (as formed) during the final step of their synthesis. Instead, a prepolymer was prepared by a living cationic polymerization of CH₂CH (OCH₂CH₂ )_n O C(O) CH₃ (n = 2 or 3). The hydrolysis of its pendant ester groups, followed by the reaction of the hydrolyzed prepolymer with each of several alkyl chloroformates of the type Cl C(O) O( CH₂CH₂O )_mR′ (m = 0, 2, or 3, R′ = Me or Et) resulted in the corresponding target polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2171–2183, 2002     

The hydroxyl radical reaction rate constant and products of methyl isobutyrate

The relative rate technique has been used to measure the rate coefficient for the reaction of the hydroxyl radical (OH) with methyl isobutyrate (MIB, (CH₃)₂ CHC(O) O CH₃) to be (1.7 ± 0.4) × 10⁻¹²cm³molecule⁻¹s⁻¹ at 297 ± 3 K and 1 atmosphere total pressure. To more clearly define MIB's atmospheric degradation mechanism, the products of the OH + MIB reaction were also determined. The observed products and their yields were: acetone (97 ± 1%, (CH₃)₂C(O)) and methyl pyruvate (MP, 3.3 ± 0.3%, CH₃C(O)C(O) O CH₃). The products' formation pathways are discussed in light of current understanding of the atmospheric chemistry of oxygenated organic compounds. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 551–557, 1999     

Supramolecular hexagonal structure of a segmented liquid crystalline polyester with allyl group as lateral substituent

The molecular structure of the phase—stable at room temperature—for the polymer with formula [ p C₆H₄ COO p C₆H₃(R) p C₆H₃(R) OOC p C₆H₄ O (CH₂)₁₀O ]_x, with R =  CH₂ CHCH₂, is reported. The cell is hexagonal (a = b = 13.43 Å, c = 33.3 Å, γ = 120°), space group P6₃, six chains per unit cell (d_calcd = 1.23 g cm⁻³). The six chains are packed together to give a bundle with the center of mass set at the origin of the unit cell. The allyl groups are placed inside the bundle, thus explaining the unexpected reactivity of the double bonds to give crosslinking when fiber samples are annealed in the solid state. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1601–1607, 1999     

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 poly(hydroxymethylene-co-ethylene) by hydrogenation of the ethylene and carbon monoxide copolymer obtained by radical initiator with Ru/α-alumina and oxygen gas permeability

A new polymer (polyalcohol) was synthesized by hydrogenation of an ethylene carbon monoxide (CO) copolymer produced by a radical method with a catalyst and H₂. The Ru/α-alumina catalyst systems showed an excellent activity for hydrogenation of the radical copolymer of CH₂CH₂ and CO. Films prepared by melting and pressing the synthesized polyalcohol had a high gas barrier property and high tensile modulus. This new polymer has hydroxymethylenic units [ CH(OH) ] and ethylenic units [ CH₂CH₂ ] in its molecular structure. The new functional polymer poly(hydroxymethylene-co-ethylene),  [ CH(OH) ]_n[ CH₂CH₂ ]_m , is amorphous and has excellent and important properties as a high oxygen gas barrier film for wrapping and storage. This may be attributed to the new structure of poly(hydroxymethylene-co-ethylene) (PHME as an IUPAC name), or ethylene methine alcohol copolymer (EMOH as a generic name), compared to the other ethylene vinyl alcohol copolymer (EVOH as a generic name),  [ CH₂CH₂ ]_m [ CH₂CH(OH) ]_n , which is used as one of the highest gas barrier polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 889–900, 1998     

Gel formation in cationic polymerization of divinyl ethers. I. 1,4-Bis(2-vinyloxyethoxy)benzene

Polymerization of 1,4-bis(2-vinyloxyethoxy)benzene (CH₂C O CH₂ CH₂ O C₆H₄ O CH₂CH₂ O CCH₂; 1 ) was investigated in CH₂Cl₂ at 0°C with the use of a variety of cationic initiators. SnCl₄, SnBr₄, AlEtCl₂, and BF₃OEt₂ (strong Lewis acids) and CF₃SO₃H (a strong protonic acid) yielded crosslinked insoluble polymers immediately after the polymerizations were initiated. The binary initiating systems such as HCl/ZnCl₂ and (C₆H₅O)₂P(O)OH/ZnCl₂ also produced insoluble poly( 1 )s. At the low initial concentration of ZnCl₂, however, the (C₆H₅O)₂P(O)OH/ZnCl₂ system gave the soluble polymers quantitatively, and gelation occurred only when the reaction mixture was stored for a long time after complete consumption of the monomer. The content of the unreacted pendant vinyl ether groups of the soluble polymers decreased with monomer conversion, and almost all the pendant vinyl ether groups were consumed in the soluble polymer obtained at 100% monomer conversion; this may be ascribed to frequent occurrence of intramolecular crosslinking. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 675–683, 1998     

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     

Macromolecular engineering of polylactones and polylactides. XXV. Synthesis and characterization of bioerodible amphiphilic networks and their use as controlled drug delivery systems

Well-defined α,ω-methacryloyl poly-ε-caprolactone (PCL) and poly(d,l )-lactide P(D,L)LA dimacromonomers have been synthesized by living ring-opening polymerization of the parent monomers initiated by diethylaluminum 2-hydroxyethylmethacrylate (Et₂Al O (CH₂)₂ O C(O) C(CH₃)CH₂) and terminated by reaction of the propagating Al alkoxide groups with methacryloyl chloride. These dimacromonomers have been copolymerized with a hydrophilic comonomer, i.e., 2-hydroxyethylmethacrylate, in bulk at 65°C by using benzoyl peroxide as a free-radical initiator. The swelling ability of the amphiphilic PHEMA/PCL or P(D,L)LA networks has been investigated in both aqueous and organic media. Effect of network composition and molecular weight of the dimacromonomer on the swelling kinetics and the equilibrium solvent uptake has been studied. Lipophilic dexamethasone acetate and the hydrophilic sodium phosphate counterpart have been incorporated into the amphiphilic gels and their release has been studied in relation to the gel characteristics. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2401–2411, 1999     

DSC and X-ray studies on side-chain crystallization of comb-like polymers

Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF₂)_nCH₂OCOCH=CH₂, (F_nA) and H(CF₂)_nCH₂OCOC(CH₃)=CH₂, (F_nMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF₁₀A and PF₁₀MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF₁₀A in 1st heating, enthalpy change H _f was 18 kJ mol^–1 and entropy change S _f was 45 J K^–1 mol^–1, while for PF₁₀MA the values H _f and S_f were 5.3 kJ mol^–1 and 14 J K^–1 mol^–1, respectively. Melted PF₈A crystallized slowly, whereas PF₈MA with same fluorocarbon chain and also both of PF₆A and PF₆MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.     

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     

Water‐Promoted Generation of a Diazairida Homobarrelene by C?C Coupling Between an Iridacyclic Alkylidene and Acetonitrile

The stable cationic iridacyclopentenylidene [Tp^Me2Ir(CHC(Me)C(Me)C H₂(NCMe)]PF₆ ( A ; Tp^Me2=hydrotris(3,5‐dimethylpyrazolyl)borate) has been obtained by α‐hydride abstraction from the iridacyclopent‐2‐ene [Tp^Me2Ir(CH₂C(Me)C(Me)C H₂)(NCMe)]. Complex A exhibits Brønsted–Lowry acidity at the Ir CH₂ and proximal (relative to Ir CH₂) methyl sites. The coordination of an extra molecule of acetonitrile to the iridium center initiates the reversible isomerization of the chelating carbon chain of A to the monodentate butadienyl ligand of complex [Tp^Me2Ir(CHC(Me)C(Me)CH₂)(NCMe)₂]PF₆, which is capable to engage in a water‐promoted C C coupling with the MeCN co‐ligands. The product is an aesthetically appealing bicyclic structure that resembles the hydrocarbon barrelene.     

Relationships between chemical structures and solubility,diffusivity, and permselectivity of 1,3-butadiene and n-butane in 6FDA-based polyimides

The solubility, diffusivity, and permselectivity of 1,3-butadiene and n-butane in seven different polyimides synthesized from 2,2-bis (3,4-carboxyphenyl) hexafluoropropane dianhydride (6FDA) were determined at 298 K. The influence of chemical structures on physical and gas permeation properties of 6FDA-based polyimides was studied. Solubility of 1,3-butadiene in 6FDA-based polyimides can be described by a dual-mode sorption model. 1,3-Butadiene-induced plasticization is considered to be associated with the increasing permeabilities of 1,3-butadiene and n-butane and the decreasing permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system containing a high concentration of 1,3-butadiene. It was found that controlling the solubility of 1,3-butadiene in an unrelaxed volume in 6FDA-based polyimides is very important to maintain the high permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system. Changing the  C(CF₃)₂ linkage to a  CH₂ ,  O linkage, removing methyl substituents at the ortho position of the imide linkage, and changing the p-phenylene linkage to an m-phenylene linkage in the main chains in some 6FDA-based polyimides are effective to decrease fractional free volume and restrict the solubility of 1,3-butadiene in the unrelaxed volume of a polymer matrix. The 6FDA-based polyimides restricting the solubility of 1,3-butadiene in an unrelaxed volume exhibit high separation performance in the 1,3-butadiene/n-butane mixed gas system compared with conventional glassy polymers and, therefore, are potentially useful membrane materials for the separation of 1,3-butadiene and n-butane in the petrochemical industry. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2941–2949, 1999     

Synthesis of Chain‐End Functionalized Polyolefins with a Bis(phenoxy imine) Titanium Catalyst

Polyethylenes and highly syndiotactic poly(propylene)s possessing chain end hydroxyl groups were synthesized by living polymerizations using L₂TiCl₂ [ 1 , L: C₆F₅NCH(2 O C₆H₃ 3 ^tBu)]/MAO and functionalized α‐olefins, H₂CCH(CH₂)_n Y [ 2 ; YOAlMe₂, n = 4 ( 2a ); YOSiMe₃, n = 9 ( 2b )]. Because the primary insertion of 2 to a cationic species L₂Ti⁺ Me ( 3 ) derived from 1 /MAO is much faster than the successive secondary insertion of 2 , addition of an equimolar amount of 2 to 3 resulted in the quantitative formation of L₂Ti⁺ CH₂ CH(Me) (CH₂)_n Y [ 4 ; YOAlMe₂, n = 4 ( 4a ); YOSiMe₃, n = 9 ( 4b )]. These cationic species 4 served as functionalized initiators for the living polymerization of both ethylene and propylene and afforded polyolefins having extremely narrow molecular weight distributions and a hydroxyl group at the initiating chain end. The terminating chain end of the syndiotactic poly(propylene)s was also functionalized by adding an excess amount of 2b as a chain end capping agent to the living L₂Ti–polymeryl species. Due to much slower insertion of the second molecule of 2b relative to the first one, the obtained polymers were end capped quantitatively by a single molecule of 2b . Telechelic syndiotactic poly(propylene)s were successfully synthesized through a living polymerization initiated by 4b and an end capping using 2b .

     

Rearrangements of (chloromethyl)organylsilanes induced by Lewis acids or by Lewis bases: Regioselective methylenation of allylic systems

In order to study the scope and mechanisms of the migration of organyl groups from silicon to its adjacent methylene carbon, a series of derivatives of the type R SiMe₂ CH₂ Cl were synthesized, where R is vinyl, benzyl, methallyl, phenylethynyl, aryloxy, and N-methylanilino. Attempts were then undertaken to induce such Si → C shifts by either the Lewis acid, methylaluminum dichloride, or the Lewis base, potassium fluoride. Under Lewis acidic conditions, only the benzyl and methylallyl groups could be induced to migrate; clearly, in the case of benzyl (and probably in the case of methallyl), migration was accompanied by allylic rearrangement to produce the o-tolyl group. Under the agency of KF, all the groups investigated underwent rearrangement to produce F SiMe₂ CH₂ R. By a crossover experiment, it was shown that, when R = aryloxy, the rearrangement occurs intermolecularly. Experimental evidence indicates that all KF-induced migrations are probably intermolecular and all MeAlCl₂-induced migrations considered here are intramolecular. The advantages for organosilicon synthesis of utilizing so-called “relay substitution reactions” with the Cl SiR₂ CH₂ Cl system are discussed: With unsymmetrical allylic systems, regioselective methylenation now becomes possible, simply by inducing the Si → C rearrangement by MeAlCl₂ or by KF.     

Aluminum five‐ and six‐coordination in bis(acetylacetonato)aminoalkoxides

Reactions of bis(acetylacetonato)aluminum(III)‐di‐μ‐isopropoxo‐di‐isopropoxo aluminum(III), [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(OPrⁱ)₂] with aminoalcohols, (HO R NR¹R²) in 1:1 and 1:2 molar ratios in refluxing anhydrous benzene yielded binuclear complexes of the types [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(O R NR¹R²)(OPrⁱ)] and [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(O R NR¹R²)₂] (R   (CH₂)₃ , R¹ = R² = H; R =  CH₂C(CH₃)₂ , R¹ = R² = H; R =  (CH₂)₂ , R¹ = H, R² =  CH₃; and R   (CH₂)₂ , R¹ = R² = CH₃), respectively. All these compounds are soluble in common organic solvents and exhibit sharp melting points. Molecular weight determinations reveal their binuclear nature in refluxing benzene. Plausible structures have been proposed on the basis of elemental analysis, molecular weight measurements, IR, NMR (¹H, ¹³C, and ²⁷Al), and FAB mass spectral studies. ²⁷Al NMR spectra show the presence of both five‐ and six‐coordinated aluminum sites. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:518–522, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10184     

Ru and Sm catalyzed polyaddition of dialdehydes to give polyesters. Application of Tishchenko type reactions to polymer synthesis

RuH₂(PPh₃)₄ catalyzed Tishchenko type polyaddition of terephthal-aldehyde gives aromatic polyester ( 1 ), which contains three structural units, [OCH₂ C₆H₄ CH₂O] ( 1a ), [OCH₂ C₆H₄ CO] ( 1b ), and [CO C₆H₄ CO] ( 1c ). ¹H-NMR spectrum shows the presence of the three units in a 1 : 2 : 1 ratio. Isophthalaldehyde also undergoes similar polyaddition to give another aromatic polyester ( 2 ), while 1,12-dodecanedial gives an aliphatic polyester ( 3 ) containing the following structural units: [OCH₂ (CH₂)₁₀ CH₂O] ( 3a ), [OCH₂ (CH₂)₁₀ CO] ( 3b ), and [CO (CH₂)₁₀ CO] ( 3c ). The above polymers have M_n of 2.7 × 10³−5.4 × 10³ and M_w of 4.3 × 10³ − 9.7 × 10³, respectively. Mixtures of terephthalaldehyde and 1,12-dodecanedial produce copolymers, which contain the units 1a–1c and 3a–3c in a random sequence. In the copolymerization, terephthalaldehyde shows a strong tendency to give 1c units, whereas 1,12-dodecanedial predominantly affords 3a units. SmI₂ also catalyzes polyaddition of terephthalaldehyde to give the corresponding polyester with M_n of 1.7 × 10³ and M_w of 3.7 × 10³, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1265–1273, 1997     

Heat capacities of perfluoropolyethers

The heat capacities at constant pressure of liquid perfluoropolyethers with different chain structures were determined above the glass transition temperature up to 480 K by means of differential scanning calorimetry (DSC). The group contributions of the  O , CF₂ , and  CF(CF₃) were calculated as a function of the temperature. Anomalous behavior of ethereal oxygen in a perfluorinated chain, as previously found for group contributions to the glass transition and to the vaporization energy, was observed also for heat capacity where the oxygen contribution is consistently lower for perfluorinated polyoxides in comparison to the hydrogenated homologous. The jump in c_p at the glass transition follows a regular behavior in the sense that ΔC_p/beadmole is within the average range found by Wunderlich for the majority of polymers. Moreover, data obtained in the present work allow the prediction of c_p of perfluoropolyethers of whatever structure between T_g and 480 K. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2073–2082, 1997     

Synthesis of vinyl ether-capped telechelic poly(tetrahydrofuran)

Vinyl ether-terminated telechelic poly(tetrahydrofuran) (poly(THF)) was synthesized by the reaction of a bifunctional living cationic polymer of THF with an excess of Na⊕⊖OCH₂CH₂ O CHCH₂ in THF at 0°C. The obtained polymer has narrow molecular weight distribution and end functionality close to two.     

Über die Entstehung von α-Keto-carbonium-Ionen bei der säurekatalysierten Hydrolyse von Diazoketonen. (Vorläufige Mitteilung)

Secondary deactivated aliphatic diazo compounds (diazo-ketones R CO CN₂ R′; diazo-esters ROOC CN₂ R′; 1, 1, 1-trifluoro-2-diazopropane) are hydrolysed by the A S_E2 mechanism comprising rate determining protonation of the substrate, followed by decomposition. Product analysis shows that the decomposition of the secondary diazonium ions is monomolecular, without intervention of a nucleophile. The corresponding primary diazo compounds (R CO CHN₂, ROOC CHN₂ and CF₃ CHN₂) are hydrolysed by the A-2 mechanism comprising preequilibrium protonation; the primary diazonium ion reacts with a nucleophile in a bimolecular displacement step. The only exception observed is found in p-nitrophenyl-diazomethane, which follows A S_E2 mechanism. The observations are discussed in terms of the stability of the corresponding secondary resp. primary α-keto-carbonium ions.