A series of polyamides n,4 (n from 2 to 12) containing one methoxy group stereoregularly attached to each a carbon atom of the diacid repeating unit has been prepared by using L-tartaric acid as the starting material. Polycondensation in a solution of bis(pentachlorophenyl) 2,3-O-dimethyl-L-tartrate with the corresponding 1 ,n-alkanediamines afforded stereoregular polymers with molecular weights between 7 X 103 and 5 X 104 depending upon the value of n, in high yields. These polyamides were fully characterized by elemental analysis and IR and 1H/13C NMR spectroscopy. They are hydrophilic, melt above 185 °C, and display large optical activity. All these properties were investigated and found to correlate well with the * To whom correspondence should be addressed.

Abstract. One-step reactive extrusion-calendering process (REX-Calendering) was used in order to obtain sheets of 1mm from two PD,L-LA extrusion grades modified with a styrene-acrylic multifunctional oligomeric agent. In a preliminary internal mixer study, torque versus time was monitored in order to determine chain extender ratios and reaction time. Once all parameters were optimized, reactive extrusion experiments were performed. Independently of the processing method employed, under the same processing conditions, PD,L-LA with the lower D enantiomer molar content revealed a higher reactivity towards the reactive agent, induced by its higher thermal sensitivity. REXCalendering process seemed to minimize the degradations reactions during processing, although a competition between degradation and chain extension/branching reactions took place in both processes. Finally, the rheological characterization revealed a higher degree of modification in the melt rheological behaviour for REX-Calendered samples.

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The synthesis of (2S,3S)-H-2,3-dimethoxy-l,4-butanediamine to be employed in the preparation of stereoregular polyamides 4,n containing two chiral carbons in the diamine repeating unit has been carried out by using L-tartaric acid as a raw material. Polycondensation in a chloroform solution of this diamine activated as the 7V,7V'-bis(trimethylsilyl) derivative with pentachlorophenyl esters of even aliphatic diacids ranging from 4 to 12 carbons afforded the title polyamides with DP" in the range 20-100 depending upon the value of n. They were characterized by elemental analysis, IR and 1H/18C spectroscopies, and powder X-ray diffraction. These highly crystalline polyamides melted in the range °C, had a pronounced affinity to water, and exhibited moderate optical activity. All these properties were investigated in relation to the molecular structure and compared with those observed for their isomeric poly[alkylene 2,3-di-Omethyl-L-tartaramide]s, on which we have recently reported in detail.

SYNOPSISStereoregular polyamides containing two chiral backbone carbons in the repeating unit were prepared by polycondensation of bis ( pentachlorophenyl ) 2,3-O-methylene-~-tartrate with 1,9 and 1,12-alcanediamines activated as N,N'-bis (trimethylsilyl) derivatives. The polymers were characterized by elemental analysis, IR, and 'H-NMR spectroscopy, and differential scanning calorimetry. Both viscosimetry and GPC were used to estimate the molecular weights which ranged between 6000 and 44000. These polytartaramides were readily soluble in chloroform, displayed moderate optical activity in solution, and formed highly crystalline films.