Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-08-17
2003-04-08
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S261000, C525S308000, C525S309000
Reexamination Certificate
active
06545098
ABSTRACT:
The present invention relates to a novel radical polymerization process a process for obtaining block copolymers.
Block polymers are usually prepared by ionic polymerization. This type of polymerization has the drawback of only allowing the polymerization of certain types of non-polar monomers, especially styrene and butadiene, and of requiring a particularly pure reaction mixture and temperatures which are often below room temperature so as to minimize parasitic reactions, thus giving severe operational constraints.
Radical polymerization has the advantage of being easily carried out without having to comply with excessive purity conditions, and at temperatures greater than or equal to room temperature. During this polymerization, macroradicals, which have a very short lifetime, recombine irreversibly by coupling or dismutation. When the polymerization takes place in the presence of several comonomers, the compositional variation of the mixture is infinitely slow compared with the lifetime of the macroradical so that the chains have a random sequence of monomer units and not a block-type sequence.
Consequently, until recently a radical polymerization process allowing block polymers to be obtained did not exist.
Since then, a new radical polymerization process has been developed, namely “controlled” or “living” radical polymerization. This controlled radical polymerization is characterized by reversible termination of the macroradicals.
At the present time, several controlled radical polymerization techniques are known, in which the ends of polymer chains may be reactivated in the form of a radical by homolytic bond (for example, C—O or C-halogen) scission.
Controlled radical polymerization therefore has the following distinct characteristics:
1. the number of chains is fixed throughout the duration of the reaction,
2. the chains all grow at the same rate, resulting in:
a linear increase in the molecular masses with conversion,
a narrow distribution of masses,
3. the average molecular mass is controlled by the monomer/chain-precursor molar ratio, and
4. the possibility of preparing block copolymers.
The controlled character is even more pronounced when the rate of consumption of the precursor is very much greater (initiation) than the rate of growth of the chains (propagation). There are cases where this is not always true and conditions 1 and 2 are not observed, nevertheless it is always possible to prepare block copolymers.
Several approaches have been described for controlling radical polymerization. The most commonly cited consists in introducing, into the mixture, counter radicals which combine reversibly with the growing macroradicals, such as, for example, nitroxyl radicals (Georges et al.,
Macromolecules,
26, 2987, (1993)). This technique is characterized by high temperatures for labilizing the C—O bond.
Another method, called
Atom Transfer Radical Polymerization,
makes use of transition metal salts combined with organic ligands and an initiator generally consisting of an organic halide; control of the polymerization is made possible by the reversibility of the C-halogen bond (K. Matyjaszewski, PCT WO 96/30421). One drawback with this polymerization is that a stoichiometric quantity of metal per chain remains.
Otsu (Otsu et al.,
Makromol. Chem. Rapid Comm.,
3, 127-132, (1982), Otsu et al. ibid, 3, 123-140, (1982), Otsu et al.,
Polymer Bull.,
7, 45, (1984), ibid, 11, 135, (1984), Otsu et al,
J. Macromol. Sci. Chem.,
A21, 961, (1984) and Otsu et al.,
Macromolecules,
19, 2087, (1989)) has shown that certain organic sulphides, particularly dithiocarbamates, allowed chains to be grown in a controlled manner under UV irradiation, according to the principle:
The principle relies on the photolysis of the C—S bond, which regenerates the carbon macroradical, on the one hand, and the dithiocarbamyl radical, on the other hand. The controlled character of the reaction is due to the reversibility of the C—S bond under UV irradiation. It is thus possible to obtain block copolymers. On the other hand, the rate of exchange in propagating species and “dormant” species is not very large compared with the rate of propagation, this having the consequence of generating relatively broad molecular mass distributions. Thus, the dispersion index (PI=M
w
/M
n
) is between 2 and 5 (Otsu et al., 25, 7/8, 643-650, (1989)).
Controlled radical polymerization has an advantage over conventional radical polymerization when it is a question of preparing low-molecular-weight functionalized chains (reactive telomers). Such polymers are desirable for specific applications such as, for example, coatings and adhesives.
Thus, when it is attempted to synthesize chains grafted with, on average, 2 functional comonomers, the fraction of chains with at most one functional site becomes large when the average degree of polymerization is less than a threshold value (e.g. 20 or 30). Controlled radical polymerization makes it possible to reduce, or even to inhibit, the formation of these oligomers having zero or one functional site which degrade the performance in terms of application.
One object of the present invention is to provide a novel radical polymerization process for the synthesis of block polymers.
Another object is to provide a radical polymerization process for the synthesis of block polymers from all types of monomers.
Another object is to provide a radical polymerization process for the synthesis of block polymers and block copolymers having a low polydispersity index.
Another object is to provide a radical polymerization process for the synthesis of block polymers containing no metal impurities deleterious to their use.
Another object is to provide a radical polymerization process for the synthesis of block copolymers, the said polymers being chain-end functionalized.
To these ends, the invention relates to a process for preparing, by radical polymerization, block polymers of general formula (I):
in which process, the following are brought into contact with each other:
an ethylenically unsaturated monomer of formula: CYY′(═CW—CW′)
a
═CH
2
,
a precursor compound of general formula (II):
a radical polymerization initiator.
The invention also relates to block polymers which can be obtained by the above process, and the polydispersivity index of which is at most 2, and more particularly at most 1.5.
Finally, the invention relates to polymers of general formulae (II) having a polydispersivity index of at most 2, and more particularly at most 1.5.
Further details and advantages of the invention will become clearer on reading the description and from the examples.
The invention first of all relates to a process for preparing, by radical polymerization, block polymers of general formula (I):
in which formula:
Z is an alkene or alkyne radical, optionally substituted with:
an optionally substituted alkyl, acyl, aryl, alkene or alkyne group,
an optionally substituted or aromatic, saturated or unsaturated, carbocycle,
an optionally substituted, saturated or unsaturated, heterocycle,
alkoxycarbonyl or aryloxycarbonyl (—COOR′), carboxyl (—COOH), acyloxy (—O
2
CR′), carbamoyl (—CONR′
2
), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (—OH), amino (—NR′
2
), halogen, allyl, epoxy, alkoxy (—OR′), S-alkyl, S-aryl or organosilyl groups,
groups having a hydrophilic or ionic character, such as the alkali metal salts of carboxylic acids or the alkali metal salts of sulphonic acid, polyalkylene oxide chains (PEO, PPO), cationic substituents (quaternary ammonium salts),
R represents:
an optionally substituted alkyl, acyl, aryl, alkene or alkyne group (i), or
an optionally substituted or aromatic, saturated or unsaturated, carbocycle (ii), or
an optionally substituted, saturated or unsaturated, heterocycle (iii),
it being possible for these groups and rings (i), (ii) and (iii) to be substituted with substituted phenyl groups or substituted aromatic groups,
Bouhadir Ghenwa
Charmot Dominique
Corpart Pascale
Zard Samir
Henderson Christopher
Rhodia Chimie
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