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  • 1
    Electronic Resource
    Electronic Resource
    The structure of 1,6-diazacyclododecane-7,12-dione, a cyclic monomeric model of polyamide 46 (1993)
    Springer
    Journal of chemical crystallography 23 (1993), S. 917-920 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 1,6-Diazacyclododecane-7,12-dione (C10H18N2O2),M r =198.27, monoclinic, one molecule in the asymmetric unit,P21/c;a=9.802(4),b=12.966(6),c=9.20(1) Å,V=1083(1) Å3,Z=4,D x =1.215(2) Mg·m−3, λ(CuKα)=1.54184 Å,μ=6.5 cm−1,F(000)=432,R=0.062 for all 866 unique observed reflection data. The molecules form hydrogen bonded stacks with two hydrogen bonds between each pair of succeeding molecules. The stacks consist of molecules with two alternating orientations, as in A-B-A-B. No strong intermolecular contacts exist between adjacent stacks, this results in a partial two-fold positional disorder of the stacks in the direction of thea-axis: two adjacent stacks can slide over half a unit cell along thea-axis without severely affecting the packing. This disorder results in very broad reflectionsh≠2n, which could only be discerned on a rotation photograph. The 12-membered ring which forms the basis of the structure has a pseudo two-fold axis through the bonds C(8)-C(10) and C(9)-C(11).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185535
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal catalytic depolymerization of polyamides (1993)
    Springer
    Polymer bulletin 31 (1993), S. 55-60 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The formation of cyclic diamides of polyamides 4,6 and 6,6 by thermal catalytic depolymerization of the corresponding polyamides was investigated. This method was optimized by changing external factors, like: concentration of catalyst; depolymerization temperature; — time; working under nitrogen flow and under a high vacuum (10-5 mbar). The catalyst sodium-2-ethylhexanoate was used to accelerate the reaction. The different multi-component depolymerization products were analyzed by reversed phase HPLC. The formation of cyclic diamides of polyamides 4,6 and 6,6 was 10, respectively 20 wt.-%, under optimum conditions, which is not sufficient to be used as feed stock for new (co)polyamides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298764
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  • 3
    Electronic Resource
    Electronic Resource
    Pivalolactone, 1 interchange reactions with polypivalolactone (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 305-319 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ester interchange, alcoholysis, and acidolysis of polypivalolactone (PPVL) were studied by melting PPVL with bisphenol diacetates, 1, 4-butanediol, or aromatic diacids. Interchange of PPVL with the diacetates and the diol occured readily, in particular in the presence of a titanium catalyst. Melting PPVL with 10 mol-% of bisphenol-Adiacetate in the presence of 0,5 wt.% tetrabutylorthotitanate resulted in an incorporation of 33% of the diacetate in the polymer chains, whereas the logarithmic viscosity number decreased by 81%. The ester interchange was suggested to proceed by an initial cleavage of ester bonds in the polymer chain of PPVL, resulting in the formation of shorter chains, followed by a reaction between the newly formed ester end-groups and initially present hydroxyl chain ends. The acidolysis of PPVL with the diacids proved to be less effective; in the case of the acidolysis of PPVL with 10 mol-% isophthalic acid, less than 1% of the diacid was incorporated in the polymer chains and a decrease in the logarithmic viscosity number of only 22% was found. Both the high stability of the ester bond in PPVL towards acids in general and the heterogeneity of these systems were supposed to cause the behaviour of PPVL with respect to acidolysis. The results concerning the interchange reactions with PPVL were compared with studies on other polyesters.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940127
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  • 4
    Electronic Resource
    Electronic Resource
    Pivalolactone, 2Part 1: cf. ref. 4. Copolyester synthesis via interchange reactions with polypivalolactone (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2807-2825 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of copolyesters via interchange reactions of polypivalolactone (PPVL) with several compounds was studied. The synthetical procedures are two-stage melt processes: in the first stage ester bonds in the polymer chain are cleaved and new groups are incorporated in the polymer chain, while in the second step condensation of the end-groups formed occurs. For the synthesis of copolymers, three procedures were used, with tetrabutyl orthotitanate as a catalyst. PPVL was heated with equimolar mixtures of bisphenol-A diacetate (BPAac) and terephthalic acid (TA), but no copolymers were formed; instead, polycondensation of BPAac with TA occurred, leaving the PPVL unaffected. From PPVL and mixtures of BPAac and dimethyl terephthalate (DMT) polymers were obtained which contained a significant amount of copolymeric sequences. However, most of the polymeric chains consisted of PPVL and poly(bisphenol-A terephthalate) blocks. Random copolymers with thermal stability were obtained after heating PPVL with bisphenol-A polycarbonate and DMT. The latter process was studied in detail by IR, DSC, and solubility and selective degradation tests. Based on the results of these studies, the reactions occurring during the three procedures were discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021941015
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of methyl groups on the thermal properties of polyesters from methyl substituted 1,4-butanediols and 4,4′-biphenyldicarboxylic acid (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 493-504 
    Details
    ISSN: 0887-624X
    Keywords: butanediol ; 4,4′-biphenyldicarboxylic acid ; characterization ; liquid crystalline polymer ; methyl substitution ; nematic ; polyester ; smectic ; synthesis ; thermal properties ; X-ray analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Results are reported on the effect of lateral methyl groups on the thermal properties of a series of polyesters prepared from diethyl 4,4′-biphenyldicarboxylate and various methyl substituted 1,4-butanediols. The diols were 1,4-butanediol; 2-methyl-1,4-butanediol; 2,2-dimethyl-1,4-butanediol; 2,3-dimethyl-1,4-butanediol; 2,2,3-trimethyl-1,4-butanediol; and 2,2,3,3-tetramethyl-1,4-butanediol. Apart from the tetramethyl derivatve, the transition temperatures of the methyl substituted polyesters were lower with respect of the unsubstituted polyester. On the basis of polarized photomicrographs, a smectic A mesophase was found for the unsubstituted polyester, whereas a nematic mesophase was observed for the 2-methyl substituted polyster. The 2,2-dimethyl, 2,3-dimethyl, and the 2,2,3-trimethyl substituted polyesters showed no liquid crystalline behavior. The 2,2,3,3-tetramethyl derivative displayed a birefringent melt phase although the DSC measurements were not unambiguous. A copolyester based on diethyl 4,4′-biphenyldicarboxylate, 1,4-butanediol, and 2,2,3,3-tetramethyl-1,4-butanediol showed a broad nematic mesophase. Further evidence for the nematic mesophase of this copolyester and the 2-methyl substituted polyester was provided by dynamic rheological experiments. Based on thermogravimetric analysis, it was concluded that the thermal stability was affected only when four methyl side groups were present in the spacer. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330316
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  • 6
    Electronic Resource
    Electronic Resource
    Pivalolactone, 3.Part 1: cf. ref.10; part 2: cf. ref. 11. Reactive blending of polypivalolactone with polycarbonate (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1577-1592 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The occurrence of interchange reactions during heating of polypivalolactone (PPVL) with three polymers and their influence on the blend properties were studied. Physical blends of PPVL and bisphenol-A polycarbonate (PC) were found to be immiscible. By heating of PPVL/PC blends in the melt at 280°C, in diphenyl ether at 260°C and in a twin-screw extruder (TSE) at 280°C partial formation of copolymers was observed, provided that tetrabutyl orthotitanate (TnBT) was added. After heating of equimolar PPVL/PC blends in a TSE for 15 min, a PPVL-PC block copolymer could be isolated containing 25 mol-% pivalolactone (PVL) units. The results from thermal analyses indicated that PPVL/PC blends had become more miscible, due to the presence of copolymers formed by interchange reactions. After heating of equimolar mixtures of PPVL and a polyarylate (PAr) in a TSE for 15 min, PPVL-PAr copolymers with 5 mol-% PVL units could be isolated. Probably due to this low degree of interchange, no effect on the miscibility of the initially immiscible PPVL/PAr blends could be observed. PPVL/poly(butylene terephthalate) (PBT) blends, obtained after heating in a TSE, decomposed at a temperature between the melting temperatures of PPVL and PBT, indicating that interchange reactions may have occurred.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950510
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