Polymer synthesis by direct polycondensation

UEDA OKADA Ordered Polymer Synthesis by Direct Polycondensation 445... 

When the ratio of template to acid is close to 0.5, the viscosity of the product is more than 3 times higher than the viscosity of the polymer obtained without the template. PEO participates in the change of local concentration by interaction with carbonyl groups, but not in the activation. Solution of LiCl in N-methylpyrrolidone with PlOCeHsls was found very effective system for synthesis of amides by the direct reaction of acids with amines in the presence of polymeric matrix. High molecular weight poly(aminoacids) obtained by direct polycondensation reaction, promoted by triphenyl phosphite and LiCl in the presence of poly(vinylpyrrolidone), were synthesized by Higashi et al The results for polymerization of L-leucine in the presence of poly(vinyl pyrrolidone) are presented in the Table 6.3. 

Yamaoka, X, Takahashi, Y., Ohta, T. et al. (1999) Synthesis and properties of multiblock copolymers consisting of poly(L-lactic acid) and poly(oxypropylene-co-oxyethylene) prepared by direct polycondensation. Journal of Polymer Science Part A Polymer Chemistry, 37, 1513-1522. 

Jikei et al. have described the synthesis of aromatic HBPA copolymers by direct polycondensation of 3-(4-aminophenoxy)benzoic acid (AB monomer) and 3,5-bis(4-aminophenoxy)benzoic acid (AB monomer) in the presence of TPP and pyridine as condensation agents [69]. The structure of resulting polymers was confirmed... 

Ogata, N., Sanui, K., Tan, S., Synthesis of Ahfatic Polyamides by Direct Polycondensation with Triphenylphosphine, Polymer, J. 1984, 16, 569. 

Imai Y, Kajiyama M, Ogata S and Kakimoto M (1985) Improved synthesis of poly-ether-aramid multi-block copolymers by direct polycondensation. Polymer J 17 1173-1178. 

Our group has initiated a synthesis of ordered polymer from nonsymmetric monomers by direct polycondensation. In the previous papers, we reported a successful synthesis of ordered polyamides (head-to-head or tail-to-tail) from a synunetric monomer and a nonsynunetric monomer, (7,2), and ordered polyamides (head-to-tail) from a synunetric monomer and a nonsynunetric monomer or a pair of two synunetric monomers (3). 

On the basis of the above findings, we initiated the synthesis of ordered (-abedef-) polymer from three nonsymmetric monomers, XabX, YcdY and ZefZ by direct polycondensation. 

Molecular composites in terms of synthesis The reinforcements are also formed by the in-situ reaction in the matrix polymers. Such methods are another way to pursue the limit of molecular dispersion of reinforcing materials. One example is found in the in-situ precipitation of reinforcing silica in polydimethyl siloxane networks with the sol-gel methods [21], Another example is the direct polycondensation of p-aminobenzoic acid or p-hydroxybenzoic acid from their monomers in solutions of polyarylate [22]. Mechanical properties of the cast films indicated increase in modulus and tensile strength at elevated temperatures. 

Several synthetic strategies have been developed to prepare phosphonated aromatic polymers, where the acid groups are attached either directly " or via spacers to an aromatic backbone. " These polymers can be prepared either by post-phosphonation of prepolymers via, e.g. transition metal catalyzed Michaelis-Arbuzov reactions and lithiation chemistiy, or by direct polymerization of phosphonated monomers via polycondensation. Both synthetic strategies then require hydrolysis of the esters to obtain the free acid. The former strategy requires the formation of C-P bonds in the polymer structure, and the latter necessitates the synthesis and purification of suitable monomers. 

A new type of polycondensation by means of phosphoms compounds in mild conditions was described by Higashi and co-workers and template effects were observed. The synthesis of polyamidation of polyamides by direct polyamidation of terephthalic acid with 4,4 -diaminodiphenylmethan was examined. P2VP, P4VP, poly(vinylpyrrolidone), and PEO were used as templates. For example, it was found that poly (terephthalamides) prepared from p-phenylenediamine and 4,4 -diaminodiphenylsulfone in the presence of PVP have much higher molecular weight than the same polymer obtained by a direct polycondensation reaction. 

Due to the pronounced tolerance of the Suzuki reaction towards additional functional groups in the monomers, precursor strategies as well as so called direct routes can be applied for polyelectrolyte synthesis. However, the latter possibility, where the ionic functionalities are already present in the monomers, was rejected. The reason is too difficult determination of molecular information by means of ionic polymers. Therefore the decision was to apply precursor strategies (Scheme 1). Here, the Pd-catalyzed polycondensation process of monomers A leads to a non-ionic PPP precursor B which can be readily characterized. Then, using sufficiently efficient and selective macro-molecular substitution reactions, precursor B can be transformed into well-defined PPP polyelectrolytes D, if appropriate via an activated intermediate C. 

In 1991 we introduced olefin metathesis as a tool for direct synthesis of PV polymers and copolymers [2]. In general, two ways exist for a metathesis chain growth process ring opening metathesis polymerization of a cyclic olefin (ROMP) and metathesis polycondensation of an acyclic diene (ADMET). We have tested both possibilities (s. Eqs. 1 2) [2-5]. A stable, tungsten based Schrock-type alkylidene complex W(=NPh - ) (=CHPh"- ) [OCMe(CF3)2l2 (THF) (described by Grubbs et al [6]) served as catalyst (Scheme 1). 

Recently, DHBCs have been used as a good stabilizer for the in-situ formation of various metal nanocolloids and semiconductor nanocrystals such as Pd, Pt [328-330], Au [280,328-330], Ag [331], CdS [332], and lanthanum hydroxide [333]. PAA-fe-PAM and PAA-fc-PHEA were used as stabihzer for the formation of hairy needle-Uke colloidal lanthanum hydroxide through the complexation of lanthanum ions in water and subsequent micelhzation and reaction [333]. The polyacrylate blocks induced the formation of starshaped micelles stabilized by the PAM or PHEA blocks. The size of the sterically stabilized colloids was controlled by simply adjusting the polymer-to-metal ratio, a very easy and versatile synthesis strategy for stable colloids in aqueous environment [333]. The concept of induced micelhzation of anionic DHBCs by cations was also apphed in a systematic study of the direct synthesis of highly stable metal hydrous oxide colloids of AP+, La +, Ni +, Zn ", Ca ", or Cu " via hydrolysis and inorganic polycondensation in the micelle core [334,335]. The AP+ colloids were characterized in detail by TEM [336], and the intermediate species in the hydrolysis process by SANS, DLS, and cryo-TEM [337]. 

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