Lactic Acid Condensation Polymers

Abstract

223 S = channel slope t = time U = mean velocity in z direction v = turbulent velocity component perpendicular to direction of w2 = mean square value of e, Y2 = mean square value of transverse spread of diffusing matter 2 = distance downstream from point a t which diffusing matter mean flow -is injected xo = scale of turbulence defined by Rdx e = kinematic eddy viscosity p = fluid density T = unit shear in fluid LITERATURE CITED (1) Dryden, H. L., IND. ENQ. ONDENSATION products or polymers of C lactic acid are important because: (a) They occur in all aqueous solutions of lactic acid containing approximately 18% lactic acid or more. (b) They are promising chemical intermediates. (c) The condensa-The preparation, properties, and reactions of condensation polymers of lactic acid are reviewed; batch and continuous methods for converting lactic acid into its condensation polymers are described. Removal of water during the dehydration or self-esterification of lactic acid is facilitated by relatively high temperature, reduced pressure, sulfuric acid or similar esterification catalyst, and an entraining agent, such as benzene or toluene. The resulting condensation polymers, which react readily with methanol, are useful for making methyl lactate. tion polymers of intermediate molecular weight can be used as such or after slight alteration as plasticizers. (d) The condensation products of higher molecular weight can be converted into useful plastics by condensation with certain vegetable oils, glycols, and other chemicals. (e) They are excellent for storing and transporting lactic acid in a highly concentrated condition; the completely polymerized linear product (I) and lactide (11) are equivalent to 125% lactic acid:Our interest in the production and properties of polymerized lactic acid was created largely by finding that the linear condensation polymers constitute an excellent starting point for making methyl lactate (19). When methyl lactate is formed by the interaction of polylactic acid and methanol, probably alcoholysis as well as esterification is involved, and only small quantities of water are formed in the reaction. Absence of water is advantageous because methyl lactate is readily hydrolyzed during distillation when appreciable quantities of water are present. Moreover, methyl lactate and water distill as an azeotropic mixture. The present paper summarizes earlier information on polylactic acid, much of which (3, 6) has not been readily available and describes both batch and continuous methods for dehydrating or polymerizing lactic acid. PREVIOUS INVESTIGATIONSAlthou h the reported findings o f previous workers are not in complete agreement, aqueous lactic acid solutions and dehydrated lactic acid appear to consist mainly of "free lactic acid:' (monomeric a-hydrox onic .acid), water, an^^^^^^ condensation or self-esterification products, such as lactyl lactic acid and lactyl lactyl lactic acid, 111: HOCH(CHs)COOCH(CHs)COOCH(CHs)COOH (111)These three components occur in various proportions, the extreme limits b...

NMR analysis and chemical shift calculations of poly(lactic acid) dimer model compounds with different tacticities

“…As expected, the 1 H and 13 C chemical shift difference between the two CH groups, 4 and 7 in Figure 1, was very small. The situation was similar for the NMR analysis and chemical shift calculations K Suganuma et al two CH 3 groups, 11 and 12, in Figure 1. Therefore, it is important to assign these peaks unambiguously.…”

“…Assignment of 1 H and 13 C NMR spectra of PLA dimer model compounds The 1 H and 13 C NMR spectra of isotactic and syndiotactic PLA dimer model compounds (1) were first obtained in CDCl 3 . As expected, the 1 H and 13 C chemical shift difference between the two CH groups, 4 and 7 in Figure 1, was very small.…”

“…1,2 Dimers, trimers and other oligomers of PLA usually occur in concentrated PLA solutions 3 and are useful materials in their own right, and have also been synthesized through polymerization [4][5][6] or degradation. 7 They can be used as building blocks for functional polymers, for example, oligomer-grafted dextran, 8 tetrafunctional oligomers 9 and oligomers encapped with sodium, 10 acrylates 11 and isocyanates.…”

Contribution of the lipophilic buffer to chiral recognition under reversed-phase conditions

“…The k values were always > 1, and excellent baseline enantioseparation was obtained for D-LA and L-LA ( Figure 3 and Table I). The LA-LA peaks in the figure arise from lactyllactic acid, which was present in the standard samples [19]. The consequence of increasing the concentration of the ion-pairing counter-ion was the simultaneous increase of k as shown in Figure 4.…”

The use of different diols in the synthesis of low-molecular-weight lactic-acid-based telechelic prepolymers

“…According to our studies, 1,4-densation, the molecular weight of poly(lactic butanediol produced prepolymers with quite good acid) is reduced by depolymerization where the molecular weights; but the prepolymers were lactide is formed. 2 amorphous, and their glass transition temperatures We have studied a two-step process for lactic were quite low. When 2 mol % of 1,4-butanediol was used in the polycondensation of lactic acid, the resulting prepolymer has a weight-average polymer contained 29.5 mol % of D-lactic acid ferential refractometer.…”