Specific functionalization of polymers by carboxyl groups

Well-defined polystyrene (PSt) with terminal carboxylic acid groups can be prepared via atom transfer radical polymerization (ATRP). One method involves the use of protected α-halocarboxylic acid initiators. Unprotected α-halocarboxylic acid initiators, such as 2-bromobutyric acid (BBA), had low initiator efficiency of 0.1−0.2 and were not effective for the ATRP of styrene. Protection of the carboxylic acid group of BBA by a trimethylsilyl, tert-butyldimethylsilyl, or tert-butyl group led to improved initiator efficiencies of ca. 0.6, 0.8, and 1, respectively, for the ATRP of styrene. Subsequent hydrolysis of the protecting groups can afford well-defined PSt with terminal carboxylic acid groups. Another method involves the use of carboxylic acid initiators with remote halogens, such as 4-(1-bromoethyl)benzoic acid and 4-(2-(2-bromopropionyloxy)ethoxy)benzoic acid. Well-defined PSt with terminal carboxylic acid groups and low polydispersities were prepared with initiator efficiencies close to 0.7.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis of Functional Polystyrenes by Atom Transfer Radical Polymerization Using Protected and Unprotected Carboxylic Acid Initiators

Zhang

Matyjaszewski

1999

“…oxy titanium carboxylates containing polymer (Ti/chain = 2.0) as well in bulk as in solution. 16 The high elastic behavior of gels based on these two materials means that the swelling proceeds preferentially by chain extension while keeping the chain-end association largely unmodified.…”

Section: Resultsmentioning

confidence: 99%

“…The same procedure applies when the alkaline-earth alkoxide is replaced by an alkoxide of alkaline metals, divalent transition metals (Cu, Zn,...), and trivalent metals like Al and Fe. 10,16 Especially in the case of alkaline and alkaline-earth metals, the ionicity of the metal-carboxylate bond is high and the ion-pair association in nonpolar environment is sensitive to the presence of small amounts of polar compounds (water, alcohol,...).10,18 Care has therefore to be taken to avoid chemical substances able to solvate the ion pairs and to limit the extent of their association. Recently, we have reported that a stoichiometric amount of a group 4 metal alkoxide was unable to quantitatively neutralize the polymer acid end groups, resulting in the absence of any cross-linking effect.…”

mentioning

confidence: 99%

Halato-telechelic polymers. 11. Viscoelastic behavior of .alpha.,.omega.-dicarboxylatopolybutadiene based on group 4 metal ions

Broze¹,

Jérôme²,

Teyssié³

et al. 1985

Self Cite

In nonpolar solvents, , -alkaline and -alkaline-earth dicarboxylatopolybutadiene (Mn 4600) leads to gel formation at concentrations as low as 1.5 g dL_1. However, any polar additive, i.e., water or alcohol, has a depressive effect on the metal-carboxylate association and the resulting gelation. The use of group 4 metal ions is an efficient way to overcome this drawback. Cross-linking of the car boxy-telechelic polymer is then promoted by a group 4 metal (Ti, Zr, Ce) alkoxide used in excess vs. the acid end groups. When the unreacted alkoxide groups are hydrolyzed into metal oxoalkoxide groupings, the gelation occurs in the presence of the alcohol formed as a byproduct and the required humidity of the medium. Cross-linking efficiency depends on the size of the group 4 cation just like in the series of alkaline and alkaline-earth cations. The deformation mechanism is controlled by the stability of the metal-carboxylate bonds and by the mean number of chain ends attached to the metal oxide aggregates. In this respect, excess alkoxide is a key parameter to impart to the solutions a broader range of rheological properties. Viscous solutions are observed at a metal-to-chain molar ratio of 0.5, whereas increasing excess of metal alkoxide is responsible for a shear-thickening behavior and finally for elastic gels.

“…[1][2][3][4][5][6][7][8][9][10][11] In our reasoning concerning the reaction mechanism, we assumed that polymerization involved insertion of the monomer on CJ metal-carbon bonds. [1][2][3][4][5][6][7][8][9][10][11] In our reasoning concerning the reaction mechanism, we assumed that polymerization involved insertion of the monomer on CJ metal-carbon bonds.…”

Section: R4nmentioning

confidence: 99%

Block Copolymerization of 3,3-Dimethyl-2-oxetanone. 1. About the Mechanism of α,α-Disubstituted β-Propiolactones Block Copolymerization

Broze¹,

Lefebvre²,

Jérôme³

et al. 1979

idenced by GC peaks at longer retention times, but these have not yet been unambiguously assigned.Fragmentation patterns show an interesting regularity (Figure 4). Under the mild conditions of chemical ionization, the macrocycles lose single or multiple T H F units, and rnJe signals appear at (M + 1) -72n, where n = 1 , 2 , 3,. , ., etc. (Table VI). This is similar to the fragmentation pattern observed earlier with tetrahydrofuran crown ethers.lS2 ConclusionMacrocyclic oligomer formation is common to EO, THF, and EO/THF polymerization systems, initiated by nonhydrolyzable, strong, protonic acids. Formation of high molecular weight linear polymers by oxonium ion ring opening and chain coupling steps is accompained by formation of macrocycles via a tail biting-back biting mechanism. In systems in which the less reactive covalent ester end group is stabilized, some linear oligomers are also found. There is a preference for certain ring sizes and compositions in THF/EO polymerizations, depending on polymerization conditions and monomer concentrations. 3,3-Dimethyl-2-oxetanone 1047