Aliphatic hyperbranched

This aliphatic hyperbranched polyester is prepared by the bulk polycondensation of 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) as AB2 monomer and 1,1,1-tris(hydroxymethyl)propane (TMP) as B3 core molecule, according to a procedure... 

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... 

Fig. 10. Complex dynamic viscosity as function of temperature for three different aliphatic hyperbranched polyesters based on bismethylol propionic acid and having different end-group structure - (O) propionate end-groups, ( ) benzoate end-groups, ( ) hydroxyl end-groups [118]...

B. Characterization of Aliphatic Hyperbranched Polyesters Molar Mass... 

Zagar E, Huskic M, Grdadolnik J, Zigrai M, Zupancic-Valant A (2005) Effect of annealing on the theological and thermal properties of aliphatic hyperbranched polyester based on 2,2-bis (methylol)propionic acid. Macromolecules 38 3933-3942... 

Hyperbranched polyethers can be synthesized via the A2+B3 approach, when diepoxides (3-24) are reacted with triols, such as TMP. Emrick et al. used 1,2,7,8-diepoxyoctane as the A2 monomer and TMP as the B3 monomer with tetra-n-butylam-monium chloride as the nucleophilic catalyst. Nucleophilic attack of the chloride ion on an epoxide at the less-hindered terminal carbon led to the formation of secondary alkoxide. Due to the equilibrium between primary and secondary alk-oxides via proton exchange, nucleophilic attack of primary alkoxides on the epoxide rings resulted in the formation of aliphatic hyperbranched polyether. As the feed ratio of the diepoxide and TMP was varied from 1.5 to 3, the resulting hb polyether contained two types of terminal units (T), one type of dendritic unit (D), and linear units (L) as shown in Scheme 4. The polydispersity index (PDI) of the polyether increased with the increase of molecular weight (from 1.5-1.8 at M = 1000 up to 5.0 at Mw = 7000). The products are viscous liquids with glass transition temperatures below room temperature. 

Polyphenylene is one of the most intractable polymers known. Hyperbranched polyphenylenes, on the other hand, exhibit excellent solubilily properties. Compared to aliphatic hyperbranched polymers, rigid monomer segments offer more open and accessible cavities where solvation can be accommodated for dissolution. The term hyperbranched polymer was first used to describe these... 

Although low-molar-mass aliphatic polyesters and unsaturated polyesters can be synthesized without added catalyst (see Sections 2.4.1.1.1 and 2.4.2.1), the presence of a catalyst is generally required for the preparation of high-molar-mass polyesters. Strong acids are very efficient polyesterification catalysts but also catalyze a number of side reactions at elevated temperature (>160°C), leading to polymers of inferior quality. Acid catalysts are, therefore, not much used. An exception is the bulk synthesis of hyperbranched polyesters reported in Section 2.4.5.1, which is carried out at moderate temperature (140°C) under vacuum in the presence of p-toluene sulfonic acid catalyst. The use of strongly acidic oil-soluble catalysts has also been reported for the low-temperature synthesis of polyester oligomers in water-in-oil emulsions.216... 

Hyperbranched Aliphatic Polyester Based on 2,2-Bis(hydroxymethyl) Propionic Acid... 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

A key monomer, namely, 2,2-bis(methylol)propionic acid (bis-MPA) has been used extensively for the preparation of hyperbranched aliphatic polyesters. Hult... 

The usefulness of the PTP concept was further demonstrated by Frechet et al. [30] in a study where hyperbranched aliphatic polyethers were synthesized from a diepoxide and a tri-functional alcohol, utilizing an A2-B3 monomer concept. 

The use of aliphatic monomers for hyperbranched polyesters has been debated because aliphatic monomers are said to be prone to thermal degradation reactions such as decarboxylation, cyclization, or dehydration [77]. The only commercial hyperbranched polymer is a hydroxy-functional aliphatic polyester, Boltorn, available from Perstorp AB, Sweden. 

Fig. 7. Examples of A B monomers used for the preparation of hyperbranched aliphatic and aromatic-aliphatic polyesters [56,62,78]...

Hult et al. [36] have described semi-crystalline hyperbranched aliphatic polyesters where the crystallinity was induced by attachment of long alkyl chains as end groups. The crystallization was affected by several factors such as length of the end groups and the molecular weight of the hyperbranched polyester. The crystallization was proposed as being either intra- or intermolecular depending on the size of the hyperbranched polyester onto which the alkyl chains were attached. 

The dilution properties of hyperbranched polymers also differ from those of linear polymers. In a comparison between two alkyd resin systems, where one was a conventional high solid alkyd and the other based on a hyperbranched aliphatic polyester, the conventional high solid alkyd was seen to exhibit a higher viscosity [113]. A more rapid decrease in viscosity with solvent content was noted for the hyperbranched alkyd when the polymers were diluted. 

The thermal stability of hyperbranched polymers is related to the chemical structure in the same manner as for linear polymers for example, aromatic esters are more stable than aliphatic ones. In one case, the addition of a small amount of a hyperbranched polyphenylene to polystyrene was found to improve the thermal stability of the blend as compared to the pure polystyrene [31]. 

A study of the PVT properties of hyperbranched aliphatic polyesters by Hult et al. [ 117] showed that these polyesters were dense structures with smaller thermal expansion coefficients and lower compressibility compared to some linear polymers. 

Fig. 11. Melt viscosity at 85 °C vs molar mass for hydroxy-functional hyperbranched aliphatic polyesters based on bismethylol propionic acid. Theoretical molar mass based on core bis-MPA ratio ( ) and Mn determined with SEC relative to linear polystyrene standards (O) [117]...

Fig.12. Comparison between a conventional high solid alkyd coating ( ) and an alkyd based on a hyperbranched aliphatic polyester ( ). Drying time as a function of molar mass [123]...

Pettersson and Sorensen have described a number of different thermoset resin structures based on hyperbranched aliphatic polyesters [123]. Their results can best be exemplified by a study on hyperbranched alkyd coating resins. A comparative study was performed between an alkyd resin based on a hyperbranched aliphatic polyester and a conventional high solid alkyd, which is a less branched structure. The hyperbranched resin had a substantially lower viscosity than the conventional resin of comparable molecular weight, that is, less solvent was needed to obtain a suitable application viscosity. The hyperbranched resin also exhibited much shorter drying times than the conventional resin, although the oil content was similar. These achievements would not have been possible without a change in architecture of the backbone structure of the resins (Figs. 12,13). 

Studies on acrylate resins [82, 124, 125] based on hyperbranched aliphatic polyesters have shown that it is possible to vary both the polarity (wetting be-... 

Commercially available hyperbranched polymers are Polyglycerol (aliphatic polyether polyol) and Polyethylenimine (aliphatic polyamine) both from Hyperpolymers, Boltom (aliphatic polyesters) from Perstorp and Hybrane (aromatic polyester amide) from DSM. 

Coullerez G, Lundmark S, Malmstroem E et al. (2003) ToF-SIMS for the characterization of hyperbranched aliphatic polyesters probing their molecular weight on surfaces based on principal component analysis (PCA). Surf Interface Anal 35 693-708... 

Frechet and coworkers reported a first example of the synthesis of a hyperbranched aliphatic polyester by polymerization of an AB inimer, i.e., 4-(hydroxyethyl)-s-caprolactone [164]. It is worth noting that the synthesis of this inimer is quite long. Since this pioneering work, other teams have reported the polymerization of a series of AB [165-167] and AB2 [168] inimers, which are shown in Fig. 38. The polymerization of these inimers can be carried out in the absence or presence of a comonomer such as sCL [167]. 

Yu X-h, Feng J, Zhuo RX (2005) Preparation of hyperbranched aliphatic polyester derived from functionalized l,4-dioxan-2-one. Macromolecules 38 6244—6247... 

---