Hyperbranched polyesters by polycondensation of fatty acid-based ABn-type monomers

In this paper, carboxylic multi-walled carbon nanotubes (MWCNTs-COOH) were modified by a series of hyperbranched polyesters (HBP) with different molecular structures (different branching degree) through surface grafting, and then the epoxy resin (EP)/carbon nanotube composites were prepared to explore the influences of structure regulation of HBP modified carbon nanotubes on the toughening performance of the composites. The results of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) of various HBP grafted carbon nanotubes confirmed that the HBP were successfully grafted onto MWCNTs-COOH via an esterification reaction between the carboxyl groups of MWCNTs-COOH and the hydroxyl groups of HBP, meanwhile, the higher the branching degree of the HBP, the higher its grafting ratio onto carbon nanotubes. Furthermore, the outcome of dynamic thermal mechanical analysis (DMA) indicated that the addition of MWCNTs-COOH increased the storage modulus and glass transition temperature (Tg) of the pure EP, and surface grafting of various HBP onto MWCNTs-COOH decreased the Tg and peak height of mechanical loss of composites. And as the branching degree of HBP increased, the interfacial bonding between MWCNTs and the EP matrix became stronger. The results of mechanical performance and morphology analysis also revealed that the addition of HBP grafted MWCNTs-COOH significantly improved its dispersion and interfacial bonding in the EP matrix, resulting in better performance in the enhancement of toughness of the composites. In addition, it was found that the higher the branching degree of HBP, the better the toughening performance of the composites.

Structure–property correlation study of hyperbranched polyurethane–urea (HBPU) coatings

Thermal field-flow fractionation (ThFFF) was used to characterize the architecture of aromatic-aliphatic polyesters with varying degrees of branching. Thermal diffusion and Soret coefficients (DT and ST, respectively) provide a novel route to polymer architecture analysis. This paper demonstrates an innovative strategy to extract architecture information from the physicochemical separation parameters embedded in ThFFF retention times without explicit separation of linear and branched samples. A Soret contraction factor (g″), defined as the ratio of the ST of a branched polymer to the ST of a molecular weight equivalent linear analogue, is introduced as a metric to indicate degree of branching (DB). This approach circumvents several challenges associated with the analysis of high molar mass polymers with a high degree of branching. The g″ value is shown to be proportional to the degree of branching for linear (DB, 0%), gradually branched (DB, <50%), hyperbranched (DB, 50%), and pseudodendritic (DB, 100%) polyesters allowing the establishment of architecture calibration curves. Furthermore, positive log(g″) values (∼0.2) at low molar mass are attributed to cyclic subpopulations. This work demonstrates the usefulness of the Soret contraction factor for statistically and hyperbranched polymer systems and its sensitivity to cyclic polymers.

To study the effect of hyperbranched polyester with different kinds of terminal groups on the thermomechanical and dielectric properties of silica–epoxy resin composite, a molecular dynamics simulation method was utilized. Pure epoxy resin and four groups of silica–epoxy resin composites were established, where the silica surface was hydrogenated, grafted with silane coupling agents, and grafted with hyperbranched polyester with terminal carboxyl and terminal hydroxyl, respectively. Then the thermal conductivity, glass transition temperature, elastic modulus, dielectric constant, free volume fraction, mean square displacement, hydrogen bonds, and binding energy of the five models were calculated. The results showed that the hyperbranched polyester significantly improved the thermomechanical and dielectric properties of the silica–epoxy composites compared with other surface treatments, and the terminal groups had an obvious effect on the enhancement effect. Among them, epoxy composite modified by the hyperbranched polyester with terminal carboxy exhibited the best thermomechanical properties and lowest dielectric constant. Our analysis of the microstructure found that the two systems grafted with hyperbranched polyester had a smaller free volume fraction (FFV) and mean square displacement (MSD), and the larger number of hydrogen bonds and greater binding energy, indicating that weaker strength of molecular segments motion and stronger interfacial bonding between silica and epoxy resin matrix were the reasons for the enhancement of the thermomechanical and dielectric properties.

Influence of shape on the reactivity and properties of dendritic, hyperbranched and linear aromatic polyesters

Randomly branched (hyperbranched) Poly(3‐hydroxybenzoate), poly(3‐Hybe), was prepared by polycondensation of silylated 3‐acetoxybenzoic acid with either silylated 3,5‐diacetoxybenzoic acid or bis(trimethylsilyl) 5‐acetoxyisophthalate. The number of branching points was varied by changing the feed ratio of difunctional and trifunctional monomers. 1H NMR and 13C NMR spectroscopy proved the nearly random incorporation of the trifunctional “branching units”. Cocondensations with small amounts of acetylated bisphenol‐P allowed one to control the degree of polymerization (DP) and to determine the DP by 1H NMR spectroscopy. However, analogous copolycondensations with silylated 2‐(4‐tert‐butylphenoxy)terephthalic acid failed. According to GPC measurements, weight‐average molecular weights above 105 were obtained. DSC measurements revealed that the glass transition temperatures (Tg's) vary largely with the degree of branching (DB) and with the nature of the end‐groups. In the case of phenolic OH and acetate end‐groups, the relationship Tg vs. number of branching points passes through a minimum.

Core-shell hyperbranched polyesters (HBPE) of third generation prepared from 2,2′-bis (hydroxymethyl) propionic acid (Bis-MPA) as an ABx monomer and N-heterocyclic (indole, piperidine and piperazine) phosphoryl dichloride as a core molecule by melt condensation process. These polymers were characterized by FT-IR, 1H NMR, 13C NMR, 31P NMR, elemental analysis, and MALDI spectroscopy. The thermal behavior of the polymers has been investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). There is no weight loss observed until 250 °C under nitrogen atmosphere. DSC showed that the glass transition temperatures was about −14 and −30 °C for the prepared core-shell HBPE. The dielectric properties such as dielectric constant and loss factor for these polyesters were also studied with respect to change of frequency (50 Hz to 5 MHz).

A novel solvent-free photosensitive polyester based on the hyperbranched aliphatic polyesters has been studied. The hyperbranched aliphatic polyesters (Polymer A), which was prepared from 2,2-dihydroxymethyl butyric acid(DMBA) containing one carboxylic group and two hydroxylic groups, Trimethylolpropane(TMP) and ptoluence sulfonic acid(p-TSA) as a catalyst, of which the degrees of branching (DB) was 0.53 according to definitions by Frechet. Followed by end-modified with maleic anhydride(MA), end-modified hyperbranched aliphatic polyesters (polymer B) with unsaturated end groups was successfully synthesized. The properties of products were characterized by FI-IR, C NMR, GPC, TGA,respectively. The UV-cured Polymer B based on polymer B, 4 wt% 1173 as photoinitiator, and Laromer R TPGDA(6:1) as reactive diluent was obtained, and was exposed for about 1s (2.2KW UV exposure apparatus). Therefore, the UV-cured Polymer B was obtained and regarded as a promising photosensitive material. Keywords-Hyperbranched aliphatic polyester; solvent-free; 2,2-dihydroxymethyl butyric acid; Photosensitive polyester; Degree of branching

A one‐pot solution polymerization under mild conditions was adapted for the synthesis of well‐defined aliphatic‐aromatic polyesters with different degrees of branching. The esterification was performed at room temperature using 4,4‐bis(4′‐hydroxyphenyl)valeric acid (AB2) and 3‐(4‐hydroxyphenyl)propionic acid (AB) as monomers. DPTS was used as a catalyst and DCC as a coupling agent. Polyesters with statistical, dendritic topology, controlled degree of branching and $\overline M _{\rm w}$ &gt; 35 000 g · mol−1 were obtained. The polymers were characterized by 1H and 13C NMR, SEC, DSC, and TGA. A strong dependence of the degree of branching and the thermal properties of the polymers depending on the AB/AB2 monomer ratio was observed.magnified image

Preparation and characterization of cross-linked poly (vinyl alcohol)/hyperbranched polyester membrane for the pervaporation dehydration of ethylene glycol solution

Photoreactive hyperbranched urethane acrylates modified with a branched saturated fatty acid

Different generations of new aliphatic hyperbranched polyesters (G1–G3), based on the polycondensation of 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer and 1,3,5-tris(2-hydroxyethyl) cyanuric acid (THECA) as a core, were modified by reacting their hydroxyl end-groups with phthalic anhydride (PG1–PG3) and trimellitic anhydride (TG1–TG3), respectively. The modified samples were identified using IR and 1H-NMR spectroscopy. The percent modification of the different generations in both systems calculated via 1H-NMR was found to be above 80%. Thermal properties of the modified hyperbranched polyesters were investigated. A series of modified hyperbranched polyesters end-capped with various amounts of methacrylate groups was synthesized by reacting the different generations of the modified polyesters in both systems with glycidyl methacrylate. In order to elucidate the structural units in the prepared methacrylated polyesters, and to calculate the degree of functionality, all samples of both systems were identified using IR and 1H-NMR. T g and hardness values were also determined.

Hyperbranched poly(ester)s (HBPE) possess attributes for applications in a number of areas which include platforms for controlled release of actives and as rheology modifiers and coalescent agents in coatings. For the latter applications, properties such as the glass transition temperature and thermal stability are important. A number of HBPEs were produced with varying composition, molecular weight, degree of branching and end-group functionality in order to determine the effect of each on the HBPE thermal and rheological properties. These materials were synthesized from trimethylolpropane and the difunctional acids; adipic, phthalic and terephthalic. The chemical structure of the resulting HBPEs was fully characterized, particularly by SEC and NMR, and the thermal properties by DSC and TG. The glass transition temperature was found to depend primarily on HBPE composition and end-group functionality. The prominent feature of the thermal degradation for the hydroxyl-capped HBPE was dehydrative ether formation while that for carboxyl-capped polymers was decarboxylation.

Immobilized Lipase B from Candida antartica (Novozyme 435) catalyzed bulk polycondensations at 70 °C for 42 h that resulted in hyperbranched polyesters with octanediol-adipate and glycerol-adipate repeat units. Instead of using organic solvents, the monomers adipic acid (A2), 1,8-octanediol (B2), and glycerol (B‘B2) were combined to form monophasic ternary mixtures. During the first 18 h of a copolymerization with monomer feed ratio (A2 to B2 to B‘B2) 1.0:0.8:0.2 mol/mol, the regioselectivity of Novozyme 435 resulted in linear copolyesters. Extending the reaction to 42 h gave hyperbranched copolymers with dendritic glycerol units. The % regioselectivity for esterifications at the primary glycerol positions ranged from 77 to 82% and was independent of glycerol content in the monomer feed. Variation of glycerol in the monomer feed gave copolymers with degree of branching (DB) from 9 to 58%. In one example, a hyperbranched copolyester with 18 mol % glycerol−adipate units was formed in 90% yield, with Mw 75 6...

Hyperbranched aliphatic copolyesters have been prepared by copolymerization of ε-caprolactone with 2,2-bis(hydroxymethyl)butyric acid, catalyzed by immobilized Lipase B from Candida antarctica (Novozyme 435) under mild conditions. Via this novel combination of ring-opening AB polymerization and AB2 polycondensation, the degree of branching (DB) and, consequently, the density of functional end groups can be controlled by the comonomer ratio in the feed (0 < DB < 0.33).