Highly branched aromatic polymers prepared by single step syntheses

Highly branched polyphenylenes, polyphenylene ethers, aromatic polyesters and polyamides synthesized from AB₂ type monomers are reviewed. Polyphenylenes were obtained by aryl-aryl coupling reactions of 3,5-dihalo-phenyl organometallic reagents. ¹³C NMR indicates about 70% branching efficiency. A T_gat 236°C was observed, but the polymer did not form films. Polyethers were prepared by oxidative coupling of 2,4,6-tribromophenol and 2,4-dibromophenol. The former monomer gave high molecular weight polymers but the latter monomer did not polymerize well. Condensation of 3,5-diaminobenzoic acid (I) and 3-aminoisophthalic acid derivatives in an amide solvent gave lyotropic hyperbranched aromatic polyamides. The GPC indicated a large degree of polymer aggregation in the amide solvent in the absence of a complexing salt.     

Comparison of glass transition and interpretation on miscibility in blends of amorphous poly(vinyl methyl ether) with highly crystallizable versus less‐crystallizable polyesters

Various phase behavior of blends of poly(vinyl ether)s with polyesters of two types (highly crystalline and less crystalline with different main‐chains) were examined using differential scanning calorimetry (DSC) and optical microscopy (OM). Effects of varying the main‐chain polarity of the constituent polyesters on the phase behavior of the blends were analyzed. Miscibility in PVME/polyester blends was found only in polyesters with backbone CH₂/CO ratio = 3.5 to 7.0). T_g‐composition relationships for blends of PVME with highly crystalline polyesters (PBA, PHS) were found to differ significantly from those for PVME blends with less‐crystalline polyesters (PTA, PEAz). Crystallinity of highly crystalline polyester constituents in blends caused significant asymmetry in the T_g‐composition relationships, and induced positive deviation of blends' T_g above linearity; on the other hand, blends of PVME with less crystalline polyesters exhibit typical Fox or Gordon‐Taylor types of relationships. The χ parameters for the miscible blends were found to range from ?0.17 to ?0.33, reflecting generally weak interactions. Phase behavior was analyzed and compared among blends of PVME with rapidly crystallizing vs. less‐crystallizing polyesters, respectively. Effects of polyesters' crystallinity and structures on phase behavior of PVME/polyester blends are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2899–2911, 2007     

A convenient room temperature polycondensation toward hyperbranched AB2‐type all‐aromatic polyesters with phenol terminal groups

As a convenient alternative to the classical melt polycondensation the one‐pot solution polycondensation of suitable AB₂ monomers under mild conditions has been successfully adapted to hyperbranched all‐aromatic polyester with phenol terminal groups. The polymerization was performed in solution at room temperature directly using commercially available 3,5‐dihydroxybenzoic acid as monomer and 4‐(dimethylamino) pyridinium 4‐tosylate as catalyst to suppress the formation of N‐acylurea. Different carbodiimides as coupling agents were investigated to find the optimal esterification conditions. The polymers have been characterized extensively and were compared with their well‐known analogs synthesized in melt. The characterization was carried out by NMR spectroscopy, size exclusion chromatography, and asymmetric flow‐field flow fractionation as an alternative separation technique for multifunctional polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5158–5168, 2009     

Synthesis and characterization of thermoplastic polyesters and polyamides from sebacyl bisketene

Sebacyl bisketene was generated in solution at ?78°C. Copolymerization in solution at 0°C with the secondary diamines, piperazine and N,N′dimethyl-1,6-hexamethylenediamine, yielded the polyamides poly(1,4-piperazylsebacyl) and poly[(methylimino)hexamethylene(methylimino)sebacyl], respectively. The polyamides were obtained in yields of 50–90%. The former had a glass transition temperature (T_g) at 30°C and a melting temperature at 165°C, whereas the latter had only a T_g at ?15°C. The polymers were insoluble in the usual polyamide solvents. Copolymerization with the diol bisphenol A yielded poly(oxy-1,4-phenyleneisopropylidene-1,4-phenyleneoxysebacyl). The polyester was obtained in yields up to 99%. Gel permeation chromatography (GPC) determinations showed molecular weights up to 50,000 when acetone was the reaction solvent but only 12,000 when tetrahydrofuran (THF) was the reaction solvent; the T_g for the polyester varied with the molecular weight with a maximum at 15°C. Tensile properties were obtained for the polyesters with molecular weights greater than 35,000.     

Designing Branched Deoxybenzoin Polyesters as Polymeric Flame Retardants

AB₂ monomers present opportunities to conduct one‐pot syntheses of highly branched or “hyperbranched” polymers, which are known for their distinct physical and chemical properties relative to linear polymers. This paper describes the synthesis of a deoxybenzoin‐containing AB₂ monomer and its use in step‐growth polymerization to prepare branched aromatic polyesters. Highly soluble deoxybenzoin polymers were obtained with degrees of branching reaching 0.36 and estimated molecular weights approaching 20 kDa. The phenolic chain ends of the polymer allowed for post‐polymerization modification by silylation and esterification chemistry. TGA and microscale combustion calorimetry revealed these novel aromatic polyesters to possess the critically important characteristics of flame‐retardant polymers, such as high char yield and low heat release. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1765–1770     

Dendritic aromatic polyamides and polyimides

The syntheses and properties of dendritic and hyperbranched aromatic polyamides and polyimides are reviewed. In addition to conventional stepwise reactions for dendrimer synthesis, an orthogonal/double‐stage convergent approach and dendrimer syntheses with unprotected building blocks are described as new synthetic strategies for dendritic polyamides. Hyperbranched polyamides and polyimides composed of various repeating units are presented. Besides the self‐polycondensation of AB₂‐type monomers, new polymerization systems with AB₄, AB₈, A₂ + B₃, and A₂ + BB′₂ monomers have been developed for hyperbranched polyamides and polyimides. The copolymerization of AB₂ and AB monomers is discussed separately with respect to the effects of branching units on the properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1293–1309, 2004     

Structure–property relationships in polyamides containing cyclohexylene or phenylene structures

Polyamides were prepared from linear, aliphatic dicarboxylic acids of six to twelve carbon atoms with 1,4-cyclohexanebis(methylamine), 1,4-cyclohexanebis (ethylamine), p-xylylenediamine, and p-phenylenebis(ethylamine). Melting points, glass transition temperatures, densities, and moisture regains were compared for the polymers to determine the relative effect of the cyclohexylene and phenylene linkages. While polyamides containing the trans-cyclohexylene group possessed higher glass transition temperatures than their aromatic counterparts, melting behavior was not as consistent. The odd-even rule, which states that polyamides with an even number of methylene linkages between the ring and the functional group melt higher than those with an odd number of such linkages, was violated in the cycloaliphatic systems. The T_g of ring-containing polyamide fibers was not dependent solely upon ring concentration, but was influenced by the molecular fit of the ringed intermediate in the polymer chains. Molecular fit appears to affect the T_g and melting point of alicyclic polyamides to a greater extent than the aromatic analogs. Differences in T_g, both within and among the polymer series, was not explained by either density or the degree of crystallinity.     

Synthesis and characterization of wholly aromatic polyesters derived from 1-phenyl-2,6-naphthalene-dicarboxylic acid and aromatic diols

A series of new wholly aromatic polyesters was synthesized by melt polycondensation of 1-phenyl-2,6-naphthalenedicarboxylic acid (PNDA) and diacetates of various aromatic diols. The aromatic diols studied are hydroquinone (HQ), methylhydroquinone (MHQ), phenylhydroquinone (PHQ), (α-phenylisopropyl)hydroquinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4-ND), and 4,4′-biphenol (BP). These polyesters were characterized for their crystallinity, glass transition temperature (T_g), melting temperature (T_m), liquid crystallinity, and thermal stability. In general, crystallinity of the polyesters are very low and the T_g values of the polyesters range from 150 to 172°C depending on the structure of aromatic diols. All of the polymers formed nematic phases above their T_m or T_g. The polyesters derived from PHQ and PIHQ are soluble in chlorinated hydrocarbon solvents. The initial decomposition temperatures of the polyesters are above 400°C under N₂ atmosphere. © 1996 John Wiley & Sons, Inc.     

Hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s: Synthesis,characterization, end‐group modification,and optical properties

Novel AB₂‐type monomers such as 3,5‐bis(4‐methylolphenoxy)benzoic acid ( monomer 1 ), methyl 3,5‐bis(4‐methylolphenoxy) benzoate ( monomer 2 ), and 3,5‐bis(4‐methylolphenoxy)benzoyl chloride ( monomer 3 ) were synthesized. Solution polymerization and melt self‐polycondensation of these monomers yielded hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s. The structure of these polymers was established using FTIR and ¹H NMR spectroscopy. The molecular weights (M_w) of the polymers were found to vary from 2.0 × 10³ to 1.49 × 10⁴ depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End‐group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4‐(decyloxy)benzoic acid and methyl red dye. The end‐capping groups were found to change the thermal properties of the polymers such as T_g. The optical properties of hyperbranched polymer and the dye‐capped hyperbranched polymer were investigated using ultraviolet‐absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414–5430, 2008     

Acid chloride‐functionalized hyperbranched polyester for facile and quantitative chain‐end modification: One‐pot synthesis and structure characterization

Carboxylic acid chloride end‐functionalized all‐aromatic hyperbranched polyesters were prepared from the bulk polycondensation of the AB₂ monomer 5‐(trimethylsiloxy)isophthaloyl dichloride. The acid chloride end functionality of the hyperbranched polyester was modified in situ with methanol and yielded methyl ester ends in a one‐pot process. Chain‐end functionalization and esterification were quantitative according to both potentiometric titration and ¹H NMR analysis. The signals of ¹H and ¹³C NMR spectra of the esterified hyperbranched polyester were fully assigned from model compounds of the focal, linear, dendritic, and terminal units. The degree of branching and molecular weight averages measured by ¹H and ¹³C NMR spectroscopy and multidetector size exclusion chromatography increased systematically with increasing polymerization temperatures between 80 and 200 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2855–2867, 2002     

Synthesis of multiblock hyperbranched‐linear poly(ether sulfone) copolymers

Hyperbranched poly(ether sulfone) was prepared in the presence of an oligomeric linear poly(ether sulfone) to generate multiblock hyperbranched‐linear (LxHB) copolymers. The LxHB copolymers were prepared in a two‐step, one‐pot synthesis by first polymerizing AB monomer to generate a linear block of a desired molecular weight followed by addition of the AB₂ monomer in a large excess (19:1, AB₂:AB) to generate the hyperbranched block. NMR integration analysis indicates that AB₂:AB ratio is independent of the reaction time. Because the molecular weight still increases with reaction time, these results suggest that polymer growth continues after consumption of monomer by condensation into a multiblock architecture. The LxHB poly(ether sulfone)s have better thermal stability (10% mass loss > 343 vs. 317 °C) and lower T_g (200 vs. > 250 °C) than the hyperbranched homopolymer, higher T_g than the linear homopolymer (<154 °C), while little difference in the solubility character was observed between the two polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4785–4793, 2008     

Complete miscibility of ternary aryl polyesters demonstrating a new criterion and horizon for miscibility characterization

A ternary miscible blend system comprising only crystallizable aryl polyesters [poly(ethylene terephthalate), poly(trimethylene terephthalate), and poly(butylene terephthalate)] was characterized with the criteria of thermal analyses, microscopy, and X‐ray characterizations. The reported ternary miscibility (in the quenched amorphous state of blends of the three aryl polyesters) was truly physical and under the condition of no chemical transesterifications; this justified that transesterification was not a necessary condition for miscibility in polyester blends in this case. This study further proposed and tested a novel concept of a new criterion for miscibility characterization for polymer blends of only crystallizable polymers. A single composition‐dependent cold‐crystallization‐temperature (T_cc) peak in blends of only semicrystalline polymers was taken as an indication of an intimate mixing state of miscibility. The theoretical background for establishing the single composition‐dependent T_cc peak as a valid miscibility criterion for crystallizable polymer blends was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2394–2404, 2003     

Novel thermotropic esters‐based polymers with broad nematic processing windows

In this study, a new series of semiflexible liquid crystalline (LC) polyesters and poly(ester‐amide)s were synthesized and characterized. Polymers based on 4‐hydroxybenzoic acid (4‐HBA), 6‐hydroxy‐2‐naphthoic acid (HNA), suberic acid (SUA), and sebacic acid (SEA) were modified with hydroquinone (HQ) and different concentrations of 4‐acetamidophenol (AP) to obtain a polyester and two poly(ester‐amide)s, respectively. All polymers were successfully prepared using conventional melt‐condensation techniques. The polymers were characterized by inherent viscosity measurements, SEC, hot‐stage polarizing microscopy, DSC, and TGA. The mechanical behavior was investigated using DMTA and tensile testing. All linear polymers have T_gs in the range of 50–80 °C and melt between 120 and 150 °C. Our polymers display good thermooxidative stabilities (5% wt loss at ～ 400 °C) and exhibit homogeneous nematic melt behavior over a wide temperature range (ΔN ～ 250 °C). The liquid crystal phase was lost when high concentrations of nonlinear monomers such as 3‐HBA (>27 mol %) and resorcinol (RC) (>23 mol %) were incorporated. The LC polyester based on 4‐HBA/HNA/HQ/SUA/SEA could easily be processed into good quality films and fibers. The films display good mechanical properties (E′ ～ 4 GPa) and high toughness, that is, ～ 15% elongation at break, at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6565–6574, 2008     

Synthesis and characterization of aromatic polymers derived from 5‐perfluoroalkylisophthalic acid

A series of polyisophthalamides and polyisophthalates having perfluorinated side chains were prepared from 5‐perfluoroalkylisophthaloyl dichlorides. The aromatic polyamides and polyarylates synthesized by conventional low temperature solution polycondensation and interfacial polycondensation, respectively, had inherent viscosities of 0.19 to 1.28 dL g⁻¹ in yields of 65 to 100%. Solubilies of the resulting polymers were improved by incorporating nonafluorobutyl groups but not improved by incorporating heptadecafluorooctyl groups. Although the effect on the glass transition temperature (T_g) of incorporating perfluoroalkyl groups into the aromatic polyamides or polyarylate backbone is great, the incorporation maintained the thermal stability of the polymers. In spite of the rigid nature of perfluoroalkyl groups, T_gs were decreased by incorporating perfluoroalkyl groups. The value of the contact angle of water on the aromatic polyamides films gradually increased with incorporation of the perfluoroalkyl groups. On the other hand, the value of the contact angle remarkably increased when perfluoroalkyl groups were incorporated into polyarylates. The Owens γs were also calculated for some aromatic polyamides by measuring contact angles of diiodomethane on the polymer films. The γs were estimated at 23‐37 mN m⁻¹ and about 10% of them were contributed by hydrogen bonding. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1135–1141, 1999     

Preparation and Properties of Novel Aromatic Polyamides from Diamines Containing 4,5-Imidazolediyl Structure

Novel aromatic polyamides were prepared from aromatic diamine containing 4,5-imidazolediyl unit, either by low temperature solution polycondensation or by direct polycondensation. Used diamines were 4,5-bis(4-aminophenyl)-2-phenylimidazole 1, 4,5-bis[4-(4-aminophenyl)]-2-(4-methylphenyl)imidazole 2 and 4,5-bis[4-(4-aminophenoxy)phenyl]-2-phenylimidazole 3. The obtained aromatic polyamides were produced with moderate to high inherent viscosity and soluble in polar aprotic solvents such as N,N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Thermogravimetric analysis showed those polymers were stable up to 422°C in nitrogen atmosphere. The glass transition temperature (T _g)s of the polymers derived from diamine 3 were in the range between 243 and 275°C, and these values were approximately 120–160°C lower than those analogue polyamide I series containing no phenoxy units. The properties of polyamide I series are also compared with those of analogue polymers that order of aromatic nuclei and amide linkage is reversible.     

Rheological and mechanical properties of antiplasticized and rubber-toughened bisphenol A polycarbonate

The addition of a high-T_g aromatic diluent to bisphenol A polycarbonate (PC) reduced T_g and melt viscosity while raising elastic modulus and yield stress substantially. Ultimate tensile elongation and impact toughness were badly affected. However, the addition to these antiplasticized blends of a small amount of a rubber modifier restored impact toughness and elongation but left the blend with increased melt fluidity and ambient stiffness re: neat PC. The key to this rebalancing of the properties of PC was found to be the disappearance of the plane strain crack instability that is a hallmark of the neat resin. The deformation mechanism in all the rubber-containing blends in all failure tests, regardless of geometric constraint and strain rate was found to be shear flow alone. The large plastic zone seen at the plane strain crack tip appears to involve rubber particle cavitation as well. © 1995 John Wiley & Sons, Inc.     

Synthesis and thermal behavior of phenylethynyl‐terminated linear and hyperbranched polyphenylquinoxalines

A phenylquinoxaline (PQ) AB monomer mixture was treated with monofunctional and difunctional end‐capping agents and with and without a coupling agent to afford phenylethynyl‐terminated linear PQ oligomers. The resulting PQ oligomers were soluble in common organic solvents and had intrinsic viscosities (IVs) of 0.21–0.30 dL/g. The glass‐transition temperature (T_g) of the diphenylethynyl‐end‐capped PQ oligomer on both sides increased the most, from 215 °C (before curing) to 251 °C (after curing). The PQ AB₂ monomer, which acted as both a coupling agent and a monomer for the hyperbranched polymer, was treated with an AB monomer and end‐capping agents to afford phenylethynyl‐terminated hyperbranched polyphenylquinoxalines (PPQs). They were also soluble in common organic solvents, had IVs of 1.00–1.65 dL/g and T_g's of 251–253 °C, and underwent exothermic cure with maxima around 412–442 °C. The T_g's of the cured hyperbranched PPQs ranged from 258 to 261 °C, depending on the number of phenylethynyl groups on the surface. After further curing, they displayed a T_g of 316 °C in one sample and turned into a fully crosslinked network. The dynamic melt viscosities of a linear oligomer (IV = 0.21 dL/g), a hyperbranched sample (IV = 1.00 dL/g), and a linear reference PPQ (IV = 1.29 dL/g) were compared with respect to the processing temperature. The PQ oligomer and hyperbranched PPQ had low melt viscosities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6318–6330, 2004     

Phenoxasilin-containing polyamides and polyesters

Silicon-containing polyamides and polyesters of a new type have been synthesized. They contain phenoxasilin rings with double-stranded structure. The polymers were synthesized by the interfacial polycondensation of 2,8-dichloroformyl-10,10-diphenylphenoxasilin with diamines and bisphenols, and were obtained in nearly quantitative yields. Their reduced viscosities were in the range of 0.53–1.47 dl g^?1 m dimethylformamide (DMF), m-cresol or chloroform. Some of the polyamides were soluble in polar aprotic solvents such as DMF and N-methyl-2-pyrrolidone (NMP) and the polyesters had good solubility in chloroform, phenol-sym tetrachloroethane (60:40 by wt %) and acidic solvents (m-cresol and nitrobenzene). The polymers hardly dissolved in cone. H₂SO₄ and some of them coloured in it. Only the polyester having sulphide bonds was soluble in benzene in addition to the above organic solvents. These polymers hardly degraded below 400° except for the polyamides derived from aliphatic diamines. The polymers from aliphatic diamines melted at 290–325°; the other polyamides and the polyesters decomposed without melting.     

Soluble and fusible polyamides and polyimides containing pyrazoline moieties and their crosslinking to heat-resistant resins

3-(4-Aminophenyl)-5-(3-aminophenyl)-2-pyrazoline as well as the 1-acetyl- or 1-benzoyl-substituted derivatives of this compound were synthesized and used for preparing a new series of polyamides and polyimides. Characterization of polymers was accomplished by inherent viscosity, ¹H-NMR, ¹³C-NMR, x-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The properties of polymers were correlated with their chemical structures. They were amorphous or microcrystalline and soluble in polar aprotic solvents, CCl₃COOH, and m-cresol. The polyamides showed an excellent solubility being soluble even in o-dichlorobenzene, 1,2-dichloroethane, and chloroform. The polymers displayed T_g at 127–163°C and softening at 150–195°C. The polyamide bearing unsubstituted pyrazoline moieties was remarkably more hydrophilic than those containing 1-acetyl- or 1-benzoyl-substituted pyrazoline segments. Upon curing, crosslinked polymers were obtained and their thermal stability was evaluated. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1353–1361, 1997     

Segmented block copolyesters using click chemistry

Copper(I) catalyzed azide‐alkyne 1,3‐Huisgen cycloaddition reaction afforded the synthesis of triazole‐containing polyesters and segmented block copolyesters at moderate temperatures. Triazole‐containing homopolyesters exhibited significantly increased (～40 °C) glass transition temperatures (T_g) relative to high temperature, melt synthesis of polyesters with analogous structures. Quantitative synthesis of azido‐terminated poly(propylene glycol) (PPG) allowed for the preparation of segmented polyesters, which exhibited increased solubility and mechanical ductility relative to triazole‐containing homopolyesters. Differential scanning calorimetry demonstrated a soft segment (SS) T_g near ?60 °C for the segmented polyesters, consistent with microphase separation. Tensile testing revealed Young's moduli ranging from 7 to 133 MPa as a function of hard segment (HS) content, and stress at break values approached 10 MPa for 50 wt % HS segmented click polyesters. Dynamic mechanical analysis demonstrated an increased rubbery plateau modulus with increased HS content, and the T_g's of both the SS and HS did not vary with composition, confirming microphase separation. Atomic force microscopy also indicated microphase separated and semicrystalline morphologies for the segmented click polyesters. This is the first report detailing the preparation of segmented copolyesters using click chemistry for the formation of ductile membranes with excellent thermomechanical response. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012