Hyperbranched polyamide

The solid-phase synthesis of dendritic polyamides was explored by Frechet et al. [49]. Inspired by the technique used by Merrifield for peptide synthesis, the same strategy was used to build hyperbranched polyamides onto a polymeric support. The idea was to ensure the preservation of the focal point and to ease the purification between successive steps. The resulting polymers were cleaved from the solid support, allowing ordinary polymer characterization. The reaction was found to be extremely sluggish beyond the fourth generation. 

In an earlier investigation by the authors (3) hyperbranched polyamides were prepared by condensing adipic acid with polyamines at 150°C. 

Nasar, A. S., Jikei, M., Kakimoto, M.aki. (2003). Synthesis and properties of polyurethane elastomers crosslinked with amine-terminated AB2-type hyperbranched polyamides, Eur. Pnlvm. 1. 39,1201-1208. 

A prominent example for a hyperbranched polypeptide is poly(lysine), which has been used as perfect dendtimer in gene delivery and other bio-inspired applications. Scholl et al. recently reviewed the field of dendritic and hyperbranched polyamides in detail. Menz and Chapman presented the first approach to hb poly(lysine) up to a molecular weight of 16l mor via condensation of the N-hydroxysuccinimide... 

Thus, the monomer 26a was polymerized with LiHMDS as a base in the presence of a core initiator and LiQ at 30°C to yield hyperbranched polyamide (HBPA) with narrow molecular weight distribution (MJM < 1.14) and a degree of branching of about 0.5. The matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that all HBPAs with different molecular weights contained the initiator unit. The value of HBPA increased linearly in proportion to the ratio of [26a](/[initiator]0 up to 40,000, while the M /M ratio remained at 1.14 or less. Therefore, the polymerization of 26a proceeds through a chain-growth polymerization mechanism from the initiator without side reaction... 

Fig. 1 Tg of hyperbranched polyamides (plane) and linear iV-alkyl poly(/n-benzamide)s as a function of M-...

Scholl M, Kadlecova Z, Klok HA (2009) Dendritic and hyperbranched polyamides. Prog Polym Sci 34 24-61... 

Chao D, He L, Berda EB, Wang S, Jia X, Wang C (2013) Multifunctional hyperbranched polyamide synthesis and properties. Polymer 54 3223-3229... 

Shabbir S, Zulfiqar S, Sarwar Ml (2011) Amine-teuminated aromatic and semi-aromatic hyperbranched polyamides synthesis and characterizatitHi. J Polym Res 18 1919—1929... 

Ohta Y, Fuji S, Yokoyama A, Furuyama T, Uchiyama M, Yokozawa T (2009) Synthesis of well-defined hyperbranched polyamides by condensation polymerization of AB2 monraner through changed substituent effects. Angew Chem Int Ed 48 5942—5945... 

Due to the shorter distance between amino and carbonyl group. In addition to numerous homopolesters having low DPs two-block copolymers either containing 3- and 4-aminobenzoyl units or different substituents or a block having a different backbone were prepared. Star-shaped polyamides were obtained from multifunctional initiators, and hyperbranched polyamides from diethyl 5-(N-methyl-amino)isophthalate (see Formula 16.8) [118]. Various details of all these CCPs were presented and discussed in two review articles [119, 120] and in five more recent publications [112-125]. 

Aliphatic hyperbranched polyesters, 56 Aliphatic isocyanate adducts, 202 Aliphatic isocyanates, 210, 225 Aliphatic polyamides, 138 Aliphatic polyesteramides, 56 Aliphatic polyesters, 18, 20, 29, 32, 87 degradable, 85 hyperbranched, 114-116 melting points of, 33, 36 structure and properties of, 40-44 syntheses of, 95-101 thermal degradation of, 38 unsubstituted and methyl-substituted, 36-38... 

To the best of our knowledge, only one other example of a carboxylic acid functionalized hyperbranched structure is known in the literature, and this concerns a polyamide [19]. The synthesis reported starts from A2 (aminofunctional) and B3 (carboxylic acid functional) units and leads to low molecular weight products due to low conversion in dilute solution. These conditions were mandatory to prevent gelation [20]. Two different approaches to the synthesis of carboxylic acid functional hyperbranched polyesteramides are presented below [21]. 

A wide range of other monomer units have been employed in the synthesis of hyperbranched macromolecules and the range of structures obtained is nearly as diverse as those for dendritic macromolecules. For example, hyperbranched polyphenylenes [93], polyesters [104, 107-109], polyethers [110-112], polyamides [113], polysilanes [114], polyetherketones [100], polycarbazoles [115], etc. [116-118] have been prepared. Interestingly, a number of groups have also used growth processes other than condensation chemistry to prepare hyper-... 

Hyperbranched polymers are formed by polymerization of AB,-monomers as first theoretically discussed by Flory. A wide variety of hyperbranched polymer structures such as aromatic polyethers and polyesters, aliphatic polyesters. polyphenylenes, and aromatic polyamides have been described in the literature. The structure of hyperbranched polymers allows some defects, i.e. the degree of branching (DB) is less than one. The synthesis of hyperbranched polymers can often be simplified compared to the one of dendrimers since it is not necessary to use protection/deprotection steps. The most common synthetic route follows a one-pot procedure " where AB,-monomers are condensated in the presence of a catalyst. Another method using a core molecule and an AB,-monomer has been described. ... 

Although rigid-rod poly(p-phenyleneterephthalamide) analogues having alkyl side chains did not contain cyclic polymers, the polycondensation of silylated m-phenylenediamine and aliphatic dicarboxyhc acid chloride afforded cyclic polyamides predominantly (Scheme 49) [187]. Furthermore, cyclic polymers were also produced in polycondensations for polyesters, poly(ether ketone)s, polyimides, and polyurethanes [183]. These examples are the products in polycondensation of AB monomers or in A2 + B2 polycondensations, but cyclization of oligomer and polymer was also confirmed in polycondensation of AB2 monomers [ 188-195] and in A2 + B3 [ 196-202] and A2 + B4 polycondensations [203-206], which afford hyperbranched polymers. 

Kim15,341 reported two related types of hyperbranched aromatic polyamides each employed amide bond formation for building block connectivity and was based on three-... 

The solid-phase preparation of hyperbranched dendritic polyamides, based on 3,5-di-aminobenzoic acid, was attempted but deemed to have severe limitations , such as the critical condensation reaction could not be forced to completion. The accessibility of chain ends within the solid support was suggested1381 to be the major obstacle to high yield conversion. 

Jikei, M., and Kakimoto, M. A. 2001. Hyperbranched aromatic polyamides prepared by direct polycondensation. High Perform. Polym., 13, S33-S43. 

Zhang RH, Yang YK, Xie XL et al (2010) Dispersion and crystallization studies of hyperbranched poly(urea-urethane)s-grafted carbon nanotubes filled polyamide-6 nanocomposites. Compos A Appl Sci Manuf 41 670-677... 

Hyperbranched and comb polymers have also been used as surface active additive. Ariura et al. synthesized by combination of anionic and cationic polymerization a monodispersed hyperbranched polystyrene [73]. The authors proved by combination of DSIMS and neutron reflectivity the preferential surface enrichment of the branched protonated macromolecules when blended with its deuterated linear polystyrene counterparts with the same molar mass. Other systems involving the segregation of the branched macromolecules in binary blends were demonstrated such as in polyamide [74] or poly (methylmethacrylate) [75]. 

Back JB, Tan LS. Quinoxaline-containing AB2 monomers for hyperbranched aromatic polyamides. US patent 6552195, assigned to the United States of America as represented by the Secretary of the Air Force, Washington, DC 2003. 

In this approach, AB2 type or other similar monomers such as AB (x = 4, 6, 8, etc.) monomers are polymerised by a polycondensation reaction. Gelation, a general problem in the polymerisation of multifunctional monomers, is avoided by the use of a dilute solution and the slow addition of monomer(s). Vegetable oil-based hyperbranched polyhydrocarbons, polyethers, polyesters, polyamides, and so on may be prepared by this method. 

Y. Ishida, A. C. F. Sun, M. Jikei and M. Kakimoto, Synthesis of hyperbranched aromatic polyamides starting from dendrons as monomers Effect of monomer multiplicity on the degree of branching , Macromolecules, 2000, 33, 2832-8. 

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