Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1996-03-28
1998-07-14
Truong, Duc
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528310, 528315, 528317, 530333, 530338, C08G 6926
Patent
active
057805792
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 PCT/FR 94/00992 filed Aug. 9, 1994.
TECHNICAL FIELD
The present invention belongs in the technical field of the synthesis of polyamino acids from amino acid N-carboxyanhydrides (referred to hereinbelow as NCAs).
Even more precisely, the present invention relates to the polymerization, in liquid medium, of NCAs by polymerization initiators of strong base type.
PRIOR ART
Polyamino acids are biocompatible and biodegradable polymers which find applications in the biomedical field. In particular, they may constitute biomaterials which are useful, for example, as starting materials for the manufacture of prostheses and implants or alternatively for use as supports which allow the release of active principles. Applications of polyamino acids as resorbable suture threads, as temporary skin substitutes or as textile fibers have also been described.
In order to be usable in these various applications, it is important for it to be possible for the polyamino acids to be in a liquid or semi-liquid form, which can be handled in the context of operations for forming finished articles, such as the formation of films, spinning, molding, etc. This therefore implies control of the intrinsic viscosity and/or of the weight-average molar mass M.sub.w of the polyamino acid synthesized.
In addition and in contrast to this, it is desirable for these polyamino acids to have a molar mass M.sub.w greater than a threshold which may be set, for example, at M.sub.w =50,000, below which they do not satisfy the structural and mechanical properties expected in the applications envisaged.
The book by H. R. Kricheldorf, ".alpha.-amino acid-N-carboxyanhydrides and related heterocycles", Springer-Verlag (1987), teaches that the polymerization of NCAs is generally carried out in liquid medium, using polymerization initiators which may be protic nucleophiles, such as water, primary amines and secondary amines, or strong bases, such as alkoxides or patent GB-996,760 proposes organometallic reagents such as trialkyllithiums or trialkylaluminums as NCA polymerization initiators.
Kricheldorf specifies (page 92) that the polymerization of NCAs, initiated by protic nucleophiles, does not give rise to high molecular weights (DPn less than 200), in contrast with initiators of the strong base type which give access to polymers of DPn greater than 200. Since these polymers are precisely those which prove to be suitable for the applications of the polyamino acids, initiation of the polymerization of NCAs by strong bases has thus been the synthetic route adopted by those skilled in the art.
However, the drawback of polymerization initiators of this type is precisely that they promote the reaction so well that neither the degree of polymerization nor the molar mass M.sub.w is any longer controlled. This thus results in extremely high reduced viscosities for the polyamino acids. This is obviously disadvantageous with regard to operations for the conversion of these polymers into manufactured products.
Consequently, one of the essential aims of the present invention is to provide a method for the synthesis of polyamino acids from NCA, in liquid medium and in the presence of initiators of strong base type: mass M.sub.w which is controllable and, advantageously, but in a nonlimiting manner, high, i.e. preferably greater than or equal to 50,000 and, even more preferably, to 80,000, finished products and, even better, which makes it possible to target a given reduced viscosity beforehand,
Thus, after considerable research and experimentation, the Applicant has, to its credit, been able to demonstrate that in order to achieve this aim, inter alia, the polymerization of the NCAs should, against all expectation, be carried out in a liquid reaction medium comprising, in particular, water and/or an alcohol.
As regards the control of the molecular mass of the polyamino acids obtained, the results thus obtained are extremely surprising. The reason for this is that it was hitherto entirely accepted in the state of the art that as long as re
REFERENCES:
patent: 3536672 (1970-10-01), Fujimoto et al.
Castan Catherine
Grosselin Jean-Michel
Jorda Rafael
Soula Gerard
Flamel Technologies (Societe Anonyme)
Truong Duc
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