Dedicated to Professor Herman F. Mark on the occasion of his 80th birthday ([>ate of receipt : Dcccm ber 17. 1974) SIJMMARY: Polydcpsipcptides with repeating units alanyl-lactyl and valyl-lactyl were synthesized by thcrmal polymeri7ation of the pcntachlorophenyl ester trifluoroacctatc salts of L-alanyl I -1actyl i.-alanyl 1.-lactic acid and i.-valyl ~.-lactyl ~.-valyl L-lactic acid.The depsidc linkages o f these monomers wcrc formed using N.N'-carbonyldiimidazolc and the pcptidc bond by coupling a A'-Boc-protected dcpside acid in thc presence of S.K'-dicycIohcxylcarbodiimide to a C-benzyl-protected dcpside amine. Alternativcly a K-Hoc-protected dcpsidc acid wascoupled by the mixed anhydridc method to the amino depside pentachlorophenyl ester. This was accomplishcd by taking advantage of thc different reaction rates of thc aminolysis of the mixed anhydridc and the pentachlorophcnyl ester. The thermal polymerization was carried out M ith the monomers dcpositcd o n a micron-sixd inorganic matrix, Kieselguhr. at temperatures between 100 and 1 2 0 T under high vacuum. Thc main fraction of polymer obtained had an average molecular weight (,D,<) of 20000-30OOO for poly(Ala-Lac) (10) and 80ooO--90000 for poly(Va1-Lac) (17). Typical yields for thcsc polymeri7ations wcrc 50 and 75"<,, respcctivcly. 7 he polLmers were found to bc frcc from racemimtion by two independent methods: total hydrolysis and hydrazinolysis

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In order to determine chemically the amino end groups present in a polyamide, the polymer was treated with a solution of 1‐fluoro‐2,4‐dinitrobenzene (FDNB) in 2,2,2‐trifluoroethanol (TFE). The resulting Nω‐[2,4‐dinitrophenyl‐(1)]‐(DNP‐) polyamide was precipitated in water at pH 3, washed free of excess reagent, redissolved in TFE, and the optical density of the solution measured at λmax = 350 nm (ε350: 17300 [1000 cm2/mole]). Both the primary and secondary amino groups could be simultaneously determined by this method, since the absorption maximum of dinitrophenylated secondary amino groups is shifted to 390 nm (ε390: 18000 [1000 cm2/mole]). Using this spectroscopic phenomenon a two‐component analytical procedure was developed. With known concentrations of dinitrophenylated primary amines, secondary amines, and nylon‐6 and nylon‐6,6 oligomers, the following analytical equations were derived: (c1: concentration of primary amino groups in mole/l; c2: concentration of secondary amino groups in mole/l; D350, D390: optical density at 350 nm and 390 nm resp.). The coefficients of variation for four different commercially available nylon‐6 fibres (unmodified and modified for dyeability) were in the range of 2.7 to 6.0%. The limiting concentration detectable was 6 × 10−7 mole DNP‐amino groups/l TFE. A kinetic analysis was performed for the reaction of FDNB with nylon‐6 and with a model compound, ε‐aminocaproic acid. Using the “absolute rate theory of Eyring”, it was found that the polymer and monomer both fulfilled the “principle of equal reactivity”. The activation parameters for the reaction were: ΔH≠ : 15.9 ± 0.9 kcal/mole, ΔG≠: 22.9 ±0.3 kcal/mole, and ΔS≠: −22.1 ± 1.9 e.u./mole.

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The saponification reaction of bis(2-hydroxyethyl) terephthalate (3) and sodium 3,5-bis(2-hydroxyethoxycarbony1)benzenesulfonate (6) was followed under pH-stat conditions in the alkaline pH range (pH 8 to 10 at 50 to 80°C) to determine the consecutive reaction rate constants for the hydrolysis of the diesters and the intermediate monoesters. The observed overall reaction rate constants were split into the individual rate constants for the hydrolysis catalyzed by the solvent, the O H -ions, the SO; groups and the COOgroups (ko. koH -, ksos. kroo-. respectively). No intermolecular catalysis by either the sulfonato or the carboxylato groups and no "autocatalysis" by the solvent was found. The activation parameters for the hydrolysis of the corresponding esters of both acids are equal; for the diesters 3 and 6: AH+=73,7 (72,O) kJ mol-' [17,6 (17,2) kcal mol-'1, AG*= 103,8 (104,7) kJ mol-' [24,8 (25,O) kcal mol-'1, AS* = -89,6 (-97,6) J mol-' K -' [-21,4(-23,3) cal mol-' K-'1; for the monoesters [terephthalic acid mono(2-hydroxyethyl) ester and 5-sodiumsulfonatoisophthalic acid mono(2-hydroxyethyl) ester]: AH*=80,4 (78,7) kJ mo1-l [19,2 (18,8) kcal mol-'1, AG+=109,3 (109,7)cal mo1-l K-'1. It is concluded that disorders in the fine structure of polyester fibers modified with sulfonato group containing comonomers may primarily be responsable for their lower hydrolytic stability and not any catalytic effects of these groups.kJ mol-' [26,1 (26,2) kcal mol-' 1, AS* = -86,3 (-93,O) J mol-' K ' [ -20,6 (-22,2) ZUSAMMENFASSUNG:Die Kinetik der Verseifungsreaktion von Terephthalsaure-bis(2-hydroxyathy1)ester (3) und Natrium-3,5-bis(2-hydroxyathoxycarbonyl)benzolsulfonat (6) wird mit Hilfe der pHstat-Technik im alkalischen pH-Bereich gemessen (pH 8 bis 10 bei 50 bis SO'C), um *) 14th communication in the series ,,Synthesefasern in der Wollindustrie"; for 13th communication see: V. Rossbach, H. Miiller, D. Nissen, Textilveredlung 9, 339 (1974).