Aliphatic Hyperbranched Polyesters Research Articles

Unanticipated Strong Blue Photoluminescence from Fully Biobased Aliphatic Hyperbranched Polyesters

Nonconventional fluorescent polymers without π-aromatic structure have attracted extensive interest in recent years. Hyperbranched polyesters are generally known because of their industrial applications; however, the luminescent properties of the polyester has not been reported. Herein, we synthesized a series of fully biobased aliphatic hyperbranched polyesters via a one-pot A2 + B3 esterification reaction. Intriguingly, the resultant hyperbranched polyesters carrying no conventional fluorescent units exhibited unexpected bright blue fluorescence under 365 nm UV light. It was found that the fluorescence intensity was enhanced with increasing solution concentrations and molecular weights of the polyesters. Moreover, the results suggested that the luminescence of polyesters could be controlled by solvents and metal ions. In particular, the fluorescence of the polyesters was extremely sensitive to Fe3+. More interesting is that the fluorescence of the polyesters showed an aggregation-induced enhanced emissi...

Alkyd resins based on hyperbranched polyesters and PET waste for coating applications

Medium oil alkyd resins based on the glycolyzed PET waste and different generations of aliphatic hyperbranched polyesters with linseed and sunflower oil fatty acids, which are of interest to the coating industry, were investigated. Different resin compositions were synthesized and characterized by IR and 1H NMR spectroscopy. The effect of oil fatty acid type, glycolyzed products, functionality of the polyols on thermal and film performance properties was studied. The onset of decomposition of all samples displayed at values above 200 °C which render them suitable for the processing requirements of most conventional coating applications. All films had good adhesion, bending, impact and ductility. The gloss and hardness increased with increasing the degree of branching and consequently, the molecular weight in the resin backbone. The presence of G3 as polyol enhanced the thermal stability and film properties of coatings.

Gold nanoparticles stabilized by amphiphilic hyperbranched polymers for catalytic reduction of 4-nitrophenol

Amphiphilic hyperbranched polymers (Hx-PEI-PEG) with polyethylene glycol (PEG) chains and low-molecular-weight polyethylenimine (PEI) conjugated to commercial aliphatic hyperbranched polyesters (Boltorn Hx) were used to stabilize gold nanoparticles (AuNPs) at the interlayer between the core and the shell. It was found that low generations of Hx-PEI-PEG such as H20-PEI-PEG and H30-PEI-PEG cannot effectively stabilize AuNPs. However, H40-PEI-PEG was both the reduction agent and the stabilizer for the formation of AuNPs, which was confirmed from the solution color change and UV–vis absorption spectra. Spherical nanosized AuNPs (below 10nm) with narrow particle size distributions were observed from the TEM images. The H40-PEI-PEG-stabilized AuNPs solution could be shelf-stored at room temperature for more than 1month. In addition, H40-PEI-PEG-stabilized AuNPs showed high catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP).

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

ABSTRACTThe rheological behavior of two series of aliphatic hyperbranched (HB) polyesters, based on 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) and di‐trimethylol propane (Di‐TMP) as a tetrafunctional core, was studied. The effect of the size (pseudo‐generation number, from second to eight) and structure on the melt rheological properties was investigated for a series of hydroxyl‐terminated HB polyesters. In addition, the influence of the nature and degree of modification of the terminal OH groups in a series of fourth‐generation polyesters end‐capped with short and long alkyl chains and some aryl groups on the rheological properties was analyzed. The time–temperature superposition procedure was applied for the construction of master curves and for the analysis of the rheological properties of HB polyesters. The data obtained from WLF analysis of the HB polyesters showed that the values of the thermal coefficient of expansion of free volume αf and the fractional free volume at the glass transition temperature, fg, increase with increasing size of the HB polyesters. It was shown that the modified HB polyesters exhibited lower Tg and TG′=G″ temperatures, above which viscous became dominant over elastic behavior. From an analysis of the master curves of the modified HB polyesters, it was observed that with increasing degree of modification, both storage and loss modules and complex dynamic viscosity and apparent energy for viscoelastic relaxation decrease, because of reduced intermolecular hydrogen interactions. They do not exhibit a plateau of rubbery behavior, which confirms that no entanglements are present and that the molar masses are below the critical molar mass. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41479.

Cell adhesion on surface patterns generated by the photocrosslinking of hyperbranched polyesters with a trisdiazonium salt

Aliphatic hyperbranched polyesters of different generation, having different nucleophilic groups (such as hydroxyl or sulfonate) in the periphery, have been photocrosslinked by using a trifunctional low molecular weight diazonium salt. The photocrosslinking process, that does not require photoinitiator, allows to prepare polymeric materials that have shown not to cause cytotoxicity when used as substrate for cell growth. Furthermore, cell adhesion studies carried out in polymeric micropatterns generated in glass by direct laser writing, show that cells preferentially proliferate on the structure demonstrating cell affinity for the material.

New aromatic–aliphatic hyperbranched polyesters with vinylic end groups of different length as modifiers of epoxy/anhydride thermosets

The synthesis and characterization of two new aromatic–aliphatic hyperbranched polyesters modified with long and short vinylic chains was reported. These hyperbranched polymers were used as toughening modifiers of epoxy/anhydride thermosets. The curing of mixtures of diglycidyl ether of bisphenol A and hexahydro-4-methylphtalic anhydride with different proportions of both hyperbranched polymers using N,N-benzyldimethylamine as catalyst was investigated by differential scanning calorimetry. The kinetic of curing process was established using an isoconversional integral procedure. The characterization of these materials was done by means of several thermal analysis techniques and their morphology was investigated by electron microscopy. The addition of highly branched structures led to homogeneous morphologies and a more toughening fracture of the thermosets in comparison to the neat epoxy/anhydride material. The modified thermosets presented slightly lower glass transition temperature than the unmodified one and the thermal stability barely changed by the addition of the modifiers.

Characterization of the commercial hyperbranched polyesters

In this paper, properties of the commercially available Boltorn? hydroxy-functional aliphatic hyperbranched polyesters of the second, third and fourth pseudo generation, were investigated. Beside that, samples of the third and fourth pseudo generation were fractionated using the precipitation fractionation method to obtain three fractions of each sample, which were also investigated in this paper. According to the results obtained by GPC analysis, molar mass and polydispersity of the investigated Boltorn? hyperbranched polyesters increased with increase of the pseudo generation number. Value of the limiting viscosity number of the investigated samples, determined using the viscosity measurements of dilute solutions of these polymers in N-methyl-2-pyrrolidone, increased with increase of the pseudo generation number. On the other side, value of the limiting viscosity number of the fractions decreased from the first up to the third fraction. The same trend was also observed for the values of the hydrodynamic diameter of parent samples and their fractions, determined by dynamic light scattering using N-methyl-2-pyrrolidone as solvent. The thermal properties of the investigated Boltorn? hyperbranched polyesters were determined by thermogravimetry in nitrogen atmosphere and it has been shown that thermal stability of these samples increased with increase of the pseudo generation number. End hydroxyl groups of the second and third pseudo generation samples were modified with ?-alanine to obtain hyperbranched samples soluble in water. That was fully accomplished only for the Boltorn? hyperbranched polyester of the second pseudo generation. On the other side, modified sample of the third pseudo generation was possible to dissolve in water only after adding small amount of the NaOH.

Melt rheology of aliphatic hyperbranched polyesters

AbstractRheological behavior in melt of aliphatic hyperbranched polyesters (AHBP), synthesized using pseudo‐one‐step and one‐step procedure, was investigated in this work. Three commercially available AHBP were also examined. Because of the presence of relatively strong hydrogen bonds between numerous end hydroxyl groups, AHBP of lower generation number, as well as the sample of tenth pseudo generation, show non‐Newtonian behavior in the entire investigated frequency and temperature region. However, for other examined AHBP, the slope of the frequency dependence of complex viscosity (η* = f(ω)) becomes smaller with the temperature increase. Therefore, samples of fourth, fifth, and sixth pseudo generations show Newtonian behavior at temperatures higher than 70°C. Value of glass transition temperature, melt flow activation energy, fractional free volume, and thermal expansion coefficient were determined for the investigated AHBP. The influence of the type of end groups on rheological properties of AHBP was also examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Modification and Methacrylation of Some New Aliphatic Hyperbranched Polyester Polyols Based on 1,3,5-Tris(2-hydroxyethyl) Cyanuric Acid (THECA) as a Core

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.

Boltorn-modified polyimide gas separation membranes

This paper describes the preparation, characterization and permeation properties of polyimide BTDA-AAPTMI (Matrimid 5218) and co-polyimide BTDA-TDI/MDI (P84) dense polymer films containing aliphatic hyperbranched polyesters, Boltorn (H40). The H40 are dispersed in the polymers at various concentrations. For Matrimid–H40 1.0 wt% membrane the nitrogen permeability increases but with significant loss in selectivity, while at higher H40 concentrations (5.0 and 10.0 wt%) the permeability becomes lower than of the pure polymer and the selectivity generally stays constant. The dispersion of various concentrations of H40 (1.0, 5.0 and 10.0 wt%) in P84 membranes decreases gas permeability in comparison to pure P84, while the selectivity generally stays constant.

Rheological Properties of Concentrated Solutions of Aliphatic Hyperbranched Polyesters

AbstractThe rheological investigation of concentrated solutions of aliphatic hyperbranched polyesters (AHBP) in N‐methyl‐2‐pyrrolidinon (NMP) is presented. Two series of hydroxy‐functional AHBP were synthesized using pseudo‐one‐step and one‐step procedure. Three commercial (Boltorn®) AHBP were also investigated. In the examined temperature region (10–50 °C), AHBP solutions (c ≤ 45 wt.‐%) exhibited Newtonian behavior. The same was observed for 50 and 55 wt.‐% solutions at T ≥ 40 °C. However, at T < 50 °C, solutions of AHBP of higher concentrations (50 and 55 wt.‐%) showed shear thinning behavior. Values of the flow activation energies were calculated for all examined AHBP. The influence of the procedure for the synthesis, concentration and temperature on rheological behavior of AHBP solutions in NMP is discussed.magnified image

Structure‐to‐Properties Relationship of Aliphatic Hyperbranched Polyesters

AbstractWe investigated the effects of annealing on the rearrangement of the H‐bond network microstructure and its influence on the thermal and rheological properties of the second pseudo‐generation hyperbranched (HB) polyester based on 2,2‐bis(methylol)propionic acid (Boltorn H20) in comparison to the fourth pseudo‐generation HB polyester (Boltorn H40). During annealing the hydroxyl groups of HB polyesters form H‐bonds with other hydroxyl or carbonyl groups. The formation of OH…OH H‐bonds is favored at shorter annealing times, higher annealing temperatures, and for low pseudo‐generation HB polyester, which has a low average molar mass, degree of branching, and core functionality. At temperatures up to 80 °C, Boltorn H20 indicates faster and more extensive H‐bond formation as compared to Boltorn H40. This is reflected in its larger cleavage enthalpies and higher elastic contribution to the viscoelastic response. At 90 °C and above, the process of H‐bond formation is delayed. Therefore, Boltorn H20 exhibits only viscous behavior in rheological measurements, and in DSC curves it shows strong exothermic transitions while heating the sample.magnified image

Boltorn-Modified Poly(2,6-dimethyl-1,4-phenylene oxide) Gas Separation Membranes

This paper describes the preparation, characterization and the permeation properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) dense polymer films containing aliphatic hyperbranched polyesters, Boltorn (H20, H30, and H40). The Boltorn are dispersed in PPO at various concentrations. The gas permeability results were very different between low and high concentration of Boltorn. The gas permeability of PPO with 1.0 wt % of Boltorn is 2−3 times higher than the pure polymer, while at higher concentration (9.1 wt %) of Boltorn the permeability becomes almost 50% of the pure polymer. The gas pair selectivity, however, stays constant. The increase in permeability at low concentration of Boltorn is due to the increase of the free volume, probably due to hydrogen bonds between Boltorn and the oxygen of PPO backbone. The decreased permeability of PPO containing higher concentration of Boltorn (9.1 wt %) is due to two reasons: decrease in free volume as determined by PALS as well as phase separation. The hyperbranced polyesters form aggregates that migrate to the top surface of the membrane.

Characterization of aliphatic hyperbranched polyesters by MALDI-TOF mass spectrometry

In this work, MALDI-TOF mass spectrometry was used for the characterization of aliphatic hyperbranched polyesters (AHBP), synthesized from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and di-trimethylolpropane. From the obtained results it was concluded that it was not possible to take complete advantages of MALDI-TOF MS in this particular case, since the AHBP used in this work were polydisperse. The intensity of the signals from the high mass tail of these samples (pseudo generation higher than four) was underestimated and insufficient to distinguish it from the baseline and to use it for the analysis of the spectra. As a consequence of that, lower values of the Mn were obtained. At the same time, Mw were also underestimated, which led to very low values of the polydispersity index. On the other hand, it was possible to obtain molar masses of individual molecules from the MALDI-TOF mass spectra of AHBP and to qualitatively determine the extent of cyclization (side reactions) at each degree of polymerization. Using the adequate set of equations and results obtained from MALDI-TOF mass spectra of AHBP, every signal from the spectra was identified. The obtained results show that formation of poly(bis-MPA), intramolecular esterification and intramolecular etherification occurred as side reactions during the synthesis of these polyesters. The relative amount of the cycles increases with the number of pseudo generation (from the second up to the fifth pseudo generation). It was also observed that the relative proportion of the signals which represent cyclic structures increases with the increasing degree of polymerization. In this work the basic principles of MALDI-TOF MS are also presented, as well as, a review of adequate published articles.

Properties of aliphatic hyperbranched polyesters in dilute solutions

The results of an investigation of the influence of the synthesis procedure, number of pseudo generations and degree of branching of hydroxy-functional aliphatic hyperbranched polyesters (AHBP) on the values of limiting viscosity number, [?], hydrodynamic radius, R?, molar mass and polydispersity index, Q, are presented in this paper. Two series of AHBP, synthesized from 2,2-bis(hydroxymethyl) propionic acid and di-trimethylolpropane using a pseudo-one-step and a one-step procedure were investigated. The obtained results show that the values of [?] and R? for all examined samples are the highest in a 0.7 mass % solution of LiCl in N,N-dimethylacetamide (LiCl/DMAc), which indicates that this solvent is the best from the investigated ones. The values of [?] in N-methyl-2-pyrrolidinone (NMP) increased up to the sixth pseudo generation, after which a slight decrease occurred as the consequence of the presence of side-reaction products, formed during the synthesis. The appearance of these side-reaction products was also confirmed from the characteristic GPC chromatograms. For the samples of AHBP synthesized using the pseudo- one-step procedure, a good linear dependence between log [?] and log Mw was obtained up to the fifth pseudo generation, when LiCl/DMAc, NMP and DMAc were used as solvents. The values of the "shrinking" factor, g?, were calculated for all investigated AHBPs.

Photoreactive hyperbranched urethane acrylates modified with a branched saturated fatty acid

Urethane acrylate resins based on partially modified aliphatic hyperbranched polyesters (HBP) were synthesized. HBP of the second and the third pseudo-generation were synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of 60% of the OH end-groups was carried out with isononanoic acid. Urethane acrylates with different degrees of acrylation were obtained by reaction of partially modified HBP and different amounts of acrylate-isocyanate adduct (NCO), which had been previously obtained by reaction of equimolar amounts of isophorone diisocyanate and 2-hydroxyethyl acrylate. The synthesized samples were characterized by FT–IR, 1H and 13C NMR spectroscopy and GPC. The rheological properties of uncured samples and the mechanical and thermal properties of UV cured urethane acrylates diluted with 20 wt.% hexanediol diacrylate were examined. The modification of the OH end-groups with isononanoic acid caused a rapid decrease in the viscosity of the HBPs. The examined properties of the urethane acrylates mainly depended on the degree of acrylation.

Thermal degradation of aliphatic hyperbranched polyesters and their derivatives

In this study results of thermal degradation of aliphatic hyperbranched polyesters, AHBP, and their derivatives, determined by non-isothermal thermogravimetric analysis in inert atmosphere (N 2) are presented. The thermal stability of linear polyester PHPA (polyhydroxypivalic acid), additionally synthesized from hydroxypivalic acid, was also studied. AHBP samples, from second to tenth pseudo-generation, were synthesized starting from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylolpropane. Modification of some selected AHBP samples was accomplished with the propionyl and benzoyl chloride, as well as with stearic acid. Thermal degradation of AHBP samples starts in the region between 250 °C and 275 °C and it ends around 430 °C. The thermal stability of AHBP samples increases with the number of end groups in the macromolecule, as well as with the modification of end groups with stearic acid and propionyl chloride. An AHBP sample of the fourth pseudo-generation, where all –OH end groups are modified with benzoyl chloride, shows lower thermal stability than the corresponding unmodified sample. The thermal stability of the linear polyester PHPA is lower than the thermal stability of the AHBP samples of the similar molar mass. The activation energies of thermal degradation for all synthesized AHBP samples were also calculated.

Characterization of commercial aliphatic hyperbranched polyesters

Commercially available Boltorn H x ( x=20, 30) hyperbranched (HB) polyesters of different theoretical core/monomer ratio (1/12 for H20 and 1/28 for H30) were characterized with respect to molar mass, composition, and structure. The results were compared to those obtained for the Boltorn H40 with a core/monomer ratio of 1/60 [Žagar E, Žigon M. Macromolecules 2002;35:9913 [11]]. The main side reaction in the pseudo one-pot synthesis of Boltorn polymers is a self-condensation of bis-MPA leading to the formation of HB structures without a core molecule. These are actually branches containing an unreacted carboxyl group. The fraction of HB structures without a core molecule increases with decreasing core/monomer ratio due to the decreasing fraction of HB structures with a core molecule. Since HB structures without a core molecule are of lower molar masses than HB structures with a core molecule, they particularly decrease the number average molar masses of the samples compared to the theoretically calculated ones. The polydispersity of Boltorn H x increases with decreasing core/monomer ratio. Some of the hydroxyl groups were found to react intramoleculary forming ether bonds. Boltorn H x polyesters have low degrees of branching due to the limited carboxyl group conversions, low DP n values, the presence of the core unit, and lower reactivity of hydroxyl groups in linear repeat units compared to those in terminal ones. The degree of branching according to Frey increases with decreasing core/monomer ratio.

UV-curable hyperbranched urethane acrylate oligomers containing soybean fatty acids

Urethane acrylate resins based on partially modified aliphatic hyperbranched polyesters (HBP) have been synthesized. HBP of the second and the third generation were synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of certain amount of OH end-groups was carried out with soybean fatty acids. The urethane acrylates with different degrees of acrylation have been obtained by reaction of partially modified HBP and different amounts of NCO adduct which had been previously obtained by reaction of equimolar amounts of isophorone diisocyanate and 2-hydroxyethyl acrylate. The synthesized samples were characterized by FT-IR, 1H and 13C NMR and GPC. The rheological properties of uncured samples and mechanical and thermal properties of UV cured urethane acrylates diluted with 20 wt.% hexanediol diacrylate were examined. The modification of OH end-groups with soybean fatty acids causes a rapid decrease in viscosity of HBP. The examined properties of urethane acrylates depend on the degree of acrylation. After irradiating, the additional cross-linking, which is caused by reaction of double bonds from unsaturated fatty acids, has also important effect on the properties of cured samples.

Synthesis of new hyperbranched urethane-acrylates and their evaluation in UV-curable coatings

Three series of hyperbranched urethane-acrylates (HB-UA), based on aliphatic hyperbranched polyesters and polyethyleneglycol acrylate, were prepared and evaluated for use in UV-curable coatings. UV-curing kinetics were monitored by FT-IR spectroscopy. The thermal and mechanical properties of UV-cured HB-UA were investigated by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) and correlated to the mechanical properties of coatings (hardness and flexibility). These new HB-UA's are very reactive and did not show oxygen inhibition. Obtained coatings have good mechanical properties and solvent resistance.