Preparation of epoxy‐ended hyperbranched polymers with precisely controllable degree of branching by thiol‐ene Michael addition

Epoxy‐ended hyperbranched polymers (EHPs) have a wide range of applications due to their outstanding performances. Because their microstructures are not positively identified, it is very difficult to ascertain the reinforcing and toughening mechanisms of EHPs and their interface interaction with other matrixes. Controllable synthesis of EHPs with precise degree of branching (DB) remains to be a major challenge. Here, a method for preparing novel nitrogen‐phosphor skeleton epoxy‐ended hyperbranched polymers (NPEHP) with controllable DB by a thiol‐ene Michael addition between thiol‐ended hyperbranched polymers (NPHSH) and glycidyl methacrylate have been firstly reported. NPHSH is synthesized by an esterification between hydroxyl‐ended hyperbranched polymers (NPHOH) and 3‐mercaptopropionic acid. NPHOH is prepared by a thiol‐ene Michael addition between methacrylate group of a monomer and thiol group of linear monomer (AB) and/or branched monomer (AB₂). The molar ratio between the AB and AB₂ monomers controls the DB of the products. The ¹H NMR spectra analysis of NPHOH shows that their experimentally determined DBs are very close to their theoretical values, indicating good controllability of their DBs. The narrow molecular weight distributions of NPHOH, NPHSH, and NPEHP suggest high efficiency of the thiol‐ene Michael addition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44277.     

Synthesis and properties of novel benzobisthiazole‐containing hyperbranched polyamides derived from 2,6‐diaminobenzo[1,2‐d:4,5‐d']bisthiazole

In this article, two novel benzobisthiazole‐containing hyperbranched polyamides with different end groups were synthesized, by adjusting the feed molar ratio of the reaction monomers, using 1,3,5‐benzenetricarboxylic acid and 2,6‐diaminobenzo[1,2‐d:4,5‐d']bisthiazole as monomers, polyphosphoric acid as solvent, and catalyst. The molecular structure of the synthesized hyperbranched polymers were speculated by ¹H‐nuclear magnetic resonance (NMR) analysis, ¹³C‐NMR analysis, and Fourier transform infrared analysis. The M_n, M_w, and DB of the carboxyl terminated polymer HB‐COOH are 3264 g/mol, 3350 g/mol, and 44.1%, respectively, with a polydispersity of 1.03. The M_n, M_w, and DB of amino terminated polymer HB‐NH₂ are 3340 g/mol, 3420 g/mol, and 41.7%, respectively, with a polydispersity of 1.02. The thermal stability of HB‐NH₂ was higher than HB‐COOH in the range of 30 °C–800 °C.These two benzobisthiazole‐containing hyperbranched polyamides were completely amorphous and soluble in DMSO. Their DMSO solutions exhibited strong blue fluorescence. The fluorescent intensity of HB‐NH₂ was higher than HB‐COOH. The prepared polymers were potential useful in the area of blue light emitting and display. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43453.     

Synthesis and characterization of hyperbranched poly(ester-amine) by Michael addition polymerization

A series of tertiary amine-based hyperbranched poly(amine-ester)s have been synthesized by Michael addition polymerization of trifunctional monomer, TMEA and difunctional monomer, diacylates in chloroform, and the resultant polymers were subsequently treated with mercaptoethenol or 1-dodecanethiol for improving stability in storage. The caption efficiency of mercaptoethanol is much better than that of 1-dodecanthiol. Kinetic study reveals that the thiol group is consumed faster than the acrylate group when the polymerization with feed molar ratio of diacrylate/TMEA = 2/1 was carried out. At initial polymerization, monomer conversion increases fast, but the molecular weights increase slowly and sharp increase of the molecular weight occurs at the final polymerization. The hyperbranched polymers were well characterized by ¹H NMR spectra and TD-SEC, and DBs of the polymers obtained are between 0.6 and 0.82, as well as the molar ratios of diacrylate/TMEA in the hyperbranched polymers are between 1.60 and 1.82. The fluorescence efficiency and quantum yields of HypET20, HypHT24 and HypDT24 has the following sequence: HypET20 > HypHT24 > HypDT24.     

Synthesis and characterization of a thermotropic liquid crystalline hyperbranched polyester

BACKGROUND: Hyperbranched polymers have received increasing attention in the fields of medicine, homogeneous catalysis and materials science. Hydroxyl‐functional aliphatic polyesters are one of the most widely investigated families of hyperbranched polymers. The research reported here is based on the preparation of a novel hyperbranched polyester and the modification of its terminal hydroxyl groups by biphenyl mesogenic units. RESULTS: 2,2,6,6‐Tetramethylolcyclohexanol as a core and 8‐[4′‐propoxy(1,1‐biphenyl)yloxy]octanoic acid as a mesogenic unit were synthesized. A hyperbranched polyester (HPE) was synthesized in one step and subsequently substituted by reaction of its terminal hydroxyl groups with the biphenyl mesogenic units to yield a novel liquid crystalline hyperbranched polyester (HPE‐LC). The chemical structures of all compounds were confirmed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. The thermal behavior and the mesogenic properties of the biphenyl mesogenic unit and HPE‐LC were investigated using differential scanning calorimetry, polarized optical microscopy and wide‐angle X‐ray diffraction. The results demonstrated that the degree of branching of the HPE is ca 0.63. Both HPE‐LC and the biphenyl mesogenic unit exhibit mesomorphic properties, but HPE‐LC has a lower isotropic transition temperature and a wider transition temperature range than the biphenyl mesogenic unit. CONCLUSION: A novel liquid crystalline hyperbranched polyester was successfully synthesized, which exhibits mesomorphic properties. This polymer has good solubility in highly polar solvents and good thermal stability. Copyright © 2009 Society of Chemical Industry     

Hyperbranched polymers from divinylbenzene and 1,3-diisopropenylbenzene through anionic self-condensing vinyl polymerization

Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer-polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li⁺]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<M_w/M_n<17).     

Preparation and characterization of a hyperbranched polyethoxysiloxane based anti‐fouling coating

A hyperbranched polyethoxysiloxane was synthesized via hydrolytic polycondensation between methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS), with hydrochloride acid as catalyst. FTIR, ¹H NMR, ²⁹Si NMR, and GPC measurements confirmed that the polyethoxysiloxane synthesized was indeed a hyperbranched polymer with a degree of branching of 0.67. It was also found that there were no silanol groups in polymer matrix. This quality can effectively enhance its storage stability. Based on the hyperbranched polyethoxysiloxane, a novel antifouling coating with high curing speed at ambient temperature was developed. The recipe and other technique parameters of the coating were revealed and investigated. Experiments indicate that the coating performs well as an antifouling agent and can be applied to various ceramic products. By using scanning electron microscope (SEM) to inspect the surface of a polished tile applied with the coating, the antifouling mechanism was studied and the results were explained in accordance with the penetrating and crosslinking of the macromolecules of hyperbrached polyethoxysiloxane into the microdefects on the surface of tiles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5818–5824, 2006     

Acetylenes with multiple triple bonds: A group of versatile An-type building blocks for the construction of functional hyperbranched polymers

AB_n-type monomers have been widely used for the synthesis of hyperbranched polymers. These monomers, however, suffer from the problems associated with the tendency of their mutually reactive A and B functional groups toward self-oligomerization. We have explored the possibility of synthesizing hyperbranched polymers using A_n-type monomers, which are stable and easy to prepare and handle, with some being even commercially available. In particular, we have tried to open new synthetic routes to hyperbranched polymers using diynes and triynes as monomers. We have developed metallic [TaBr₅, Cp^∗Ru(PPh₃)₂Cl, etc.] and nonmetallic catalysts (piperidine, DMF, etc.) for polycyclotrimerization, polycycloaddition and polycoupling of the acetylenic monomers. We have synthesized a variety of new hyperbranched polymers including polyarylenes, polytriazoles and polydiynes with high molecular weights and excellent solubility in high yields. The polymers exhibit an array of functional properties such as sensitive photonic response, high light refractivity, large optical nonlinearity, high thermal stability, strong optical limiting power and unusual aggregation-enhanced light emission. Utilizing these unique properties, we succeeded in generating fluorescent images, honeycomb patterns, polymer nanotubes, ferromagnetic ceramics, and nanoparticle catalysts.     

Design,synthesis and polymerization of highly branched pseudodendrimers through tandem reactions

BACKGROUND: Pseudodendrimers are hyperbranched polymers which are isomeric with dendrimers, that is, each repeat unit is either fully reacted or only singly reacted. The careful design of an ABB′ monomer leads to higher branching by virtue of tandem reactions that increase the reactivity of linear units during polymerization, leading to fully reacted repeat units. The resulting polymers are predicted to be very highly branched, and in the optimum case, pseudodendrimers. RESULTS: Our work shows that 6‐amino‐3‐bromophthalide leads to a highly branched polymer via bromohydrin decomposition during polymerization, giving polymers of M? = of 3000 and a polydispersity index of 1.03. Our findings indicate a degree of branching of 0.84. The synthesis of similar polymers using different techniques confirms our proposed intermediate. CONCLUSION: We have demonstrated a new class of hyperbranched polymers which are highly branched, and may be considered pseudodendrimers. Copyright © 2009 Society of Chemical Industry     

Phase separation in epoxy resin‐reactive dendritic hyperbranched polymer blends

Equilibrium phase diagrams in composition‐conversion space have been calculated for stoichiometric blends of an epoxy resin with a diamine hardener and dendritic hyperbranched polymers, to which various numbers of epoxy groups have been grafted. An attempt has been made to incorporate both the effects of the polydispersity of the resin and the reactivity of the functionalized hyperbranched polymers for any given value of the interaction parameter. However, if the reactivities of all the epoxy groups are comparable, the presence of a highly functionalized modifier is expected to lead to a reduction of the gel point conversion and a narrowing of the composition‐conversion window available for cure induced phase separation. The experimental cloud point data are consistent with the model, although they sugget that the functionalized hyperbranched polymers may be significantly less reactive than the resin. Moreover, in the present system, the influence of functionalization on the phase behavior is also strongly linked to the accompanying changes in the interaction parameter.     

Synthesis of multi‐arm star polystyrene with hyperbranched polyester initiators by atom transfer radical polymerization

Multi‐arm star polystyrenes with hyperbranched polyester (HP3) core were prepared by atom transfer radical polymerization (ATRP). The structures of the polymers were investigated with FTIR and ¹H NMR. GPC results showed that the resultant polymers had relatively broad polydispersity indices that arouse from the macromolecular initiator (HP3‐Br). The thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis indicated that polystyrene star polymers had only the glass transition temperatures (T_g), which changes with the weight ratio of multi‐functional macroinitiator‐to‐monomer. In addition, these star polymers could form the spherical micelles in the selected solvent (THF/n‐hexane). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 728–733, 2006     

Bio-based hyperbranched polyurethanes for surface coating applications

High performance vegetable oil based hyperbranched polymers are not only interesting but also very useful with respect to current scenario of advanced coating materials. So in the present study hyperbranched polyurethanes have been synthesized from the monoglyceride of Mesua ferrea L. seed oil, poly(?-caprolactone)diol, 2,4-toluene diisocyanate and glycerol without using any catalyst by a two-step one pot A₂ + B₃ approach. The linear analog (neglecting little possible branching due to different components of monoglyceride) of the hyperbranched polyurethane has also been prepared by the same method without using glycerol, just to compare with hyperbranched polymer. The formation of polymers was confirmed by FTIR, ¹H NMR, UV and SEM studies and measurements of hydroxyl value, solubility and viscosity. TGA results indicated the high thermal stability of hyperbranched and linear polymers (210–220 °C). The properties like tensile strength, impact strength, hardness, adhesion, flexibility, gloss, elongation at break and chemical resistance were influenced by the hard segment content of the polymers. The hyperbranched polyurethane with 30% hard segment content showed the optimum properties. The values of hydrodynamic diameter of hyperbranched polymers compared to the linear analog support the hyperbranched formation. Thus it confirms the formation of mechanically strong and thermally stable hyperbranched polyurethane coating materials from a vegetable oil.     

Facile and efficient synthesis of hyperbranched polyesters based on renewable castor oil

Hyperbranched polyesters with thioether linkages were facilely prepared from methyl 10‐undecenoate, a castor oil‐derived renewable chemical. The monomer was obtained in excellent yield through thiol–ene click chemistry in the presence of catalytic amounts of photoinitiator under UV irradiation. Subsequent bulk polycondensation via a transesterification process catalyzed by Ti(OBu)₄, Sb₂O₃ or Zn(OAc)₂ gave hyperbranched polyesters with high molecular weights and unusual crystalline properties. The degree of branching in the range 0.45 ? 0.54 calculated from quantitative ¹³C NMR spectroscopy and low inherent viscosities of 0.16 ? 0.25 dL g^?1 strongly confirmed the hyperbranched structures of the resultant polymers. © 2012 Society of Chemical Industry     

Novel hyperbranched poly(phenylene oxide)s with phenolic terminal groups: synthesis, characterization, and modification

Novel hyperbranched poly(phenylene oxide)s (HPPOs) with phenolic terminal groups were prepared from 4-bromo-4′,4″-dihydroxytriphenylmethane via a modified Ullmann reaction. This monomer was treated with potassium carbonate or sodium hydroxide as a base and copper chloride as a catalyst in an aprotogenic solvent, either dimethylsulphoxide (DMSO) or sulfolane. The sulfolane/NaOH system at higher temperature led to more rapid polymerization, and a relative high molecular weight. The degrees of branching of these HPPOs from the DMSO/K₂CO₃ and sulfolane/NaOH systems were 71 and 48%, respectively, as determined by ¹H NMR integration experiments. The phenolic terminal groups underwent facile modification, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the solubility of the hyperbranched poly(phenylene oxide)s. The resulting polymers were characterized by NMR, Fourier transform infrared, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Preparation and characterization of fluorescent hyperbranched polyether

A new kind of fluorescent hyperbranched polymers was prepared by an end-capping approach, i.e., the hyperbranched poly(hydroxyl ether) was end capped with p-N,N-dimethylaminobenzaldehyde. The resulting polymers fluoresce yellow-green in solid and in solution. The maximum excitation and emission wavelengths in ethanol are 310 ± 10 and 360 ± 10 nm, respectively. Hyperbranched polyethers with various densities of chromophore groups showed different fluorescence intensities at the same concentration of chromophore groups. The fluorescent hyperbranched polyether with a high density of chromophore groups can form intramolecular excimers. The fluorescence signal of the resulting polymer increases with pH and passes through a maximum at 7.2–8.5 and then decreases gradually. Furthermore, the peak at 360 nm shifts to 405 nm with increasing pH. The fluorescence can be quenched by transition metal cations such as Cu²⁺ and Fe³⁺, while the alkali and alkaline earth metal cations and Ni²⁺ and Co²⁺ have little effect on the fluorescence intensity.     

Preparation of hyperbranched polymers through ATRP of in situ formed AB* monomer

The self‐condensing vinyl polymerization of an AB* monomer formed in situ by atom transfer radical addition from divinylbenzene (DVB) and (1‐bromoethyl)benzene (BEB) using atom transfer radical polymerization technique was studied. The catalyst concentration has a dramatic effect on polymerization. To study the polymerization mechanism and to achieve high molecular weight polymer, the polymerization was carried out in bulk with a catalyst to monomer ratio, 2,2′‐bipyridine to DVB, of 0.2 at 90°C. Proton nuclear magnetic resonance (¹H NMR) spectroscopy and size‐exclusion chromatography coupled with multiangle laser light scattering were used to analyze the polymerization aliquots and the obtained polymer. The intrinsic viscosities of the prepared polymers were also measured. Experimental results, from the comparison of the apparent molecular weights measured by size‐exclusion chromatography with the absolute values measured by multiangle laser light scattering as well as viscosity measurements, indicate the existence of hyperbranched structures in the prepared polymers. In sharp contrast to hyperbranched polymers from AB* monomer preprepared, hyperbranched ploy(divinylbenzene) prepared at equimolar amount of DVB and BEB has numerous residual pendant vinyl groups rather than only one double bond at its focal point. The hyperbranched polymers show relatively narrow molecular weight distribution (2.13–3.77) and exhibit excellent solubility in common organic solvents such as acetone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 850–856, 2006     

Hyperbranched polymers containing oxazoline monomers and succinic anhydride: Applications in fast drying,low solvent coating formulations

Melt-polycondensation of succinic acid anhydride with oxazoline-based diol monomers gave hyperbranched polymers with carboxylicacids terminal groups. ¹H NMR and quantitative ¹³C NMR spectroscopy coupled with DEPT-135 ¹³C NMR experiment showed high degrees of branching (over 60%). Esterification of the acid end groups by addition of citronellol at 160 °C produced novel white spirit soluble resins which were characterized by Fourier transform-infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Blends of the new hyperbranched materials with commercial alkyd resins resulted in a dramatic, concentration dependent drop in viscosity. Solvent-borne coatings were formulated containing the hyperbranched polymers. Dynamic mechanical analysis studies revealed that the air drying rates of the new coating systems were enhanced compared with identical formulations containing only commercial alkyd resins.     

Synthesis and characterization of the environmental‐sensitive hyperbranched polymers as novel carriers for controlled drug release

Novel hyperbranched polymers, which contain a hydrophobic branched poly(p‐(chloromethy)styrene) (PCMS) core and poly(N,N‐dimethylaminoethyl methacrylate) (PDMA) shell that exhibited environmental sensitivity, have been synthesized by atom transfer radical polymerization (ATRP). At first, a hyperbranched polymer (PCMS) core is obtained via ATRP of p‐(chloromethy)styrene (CMS), which may act as an “inimer”‐monomer and initiator. Then the modified hyperbranched polymers having different average arm length consisting of PCMS and PDMA are synthesized by ATRP using anterior PCMS as macroinitiators. Their macromolecular structures are characterized by FTIR and ¹H NMR. Using chlorambucil as a model drug, the behaviors of the controlled drug release from the environmental‐sensitive hyperbranched polymers with different average chain length of PDMA and degree of branching are studied. The data demonstrate that the rate of the drug release can be effectively controlled by pH value, and these environmental‐sensitive hyperbranched polymers have the potential to be used as novel carriers in some controlled drug release systems in the future. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 311–316, 2006