The effect of compositions and combinations of the reactants upon the copolycondensation of isophthalic acid/terephthalic acid with a combination of hydroquinones and bisphenols by tosyl chloride/dimethylformamide/pyridine

Copolycondensation of isophthalic acid (IPA)/terephthalic acid (TPA) with various combinations of 2,2‐bis(4‐hydroxyphenyl)propane (BPA) and hydroquinones (HQs) or bisphenols (BPs) was conducted to study the effects of the compositions of IPA/TPA and of BPA/HQs or BPA/BPs upon the reaction. Different from homopolycondensation of each of diol components examined where most of the reaction was facilitated by lower contents of IPA at about 70 mol %, the copolycondensation was influenced by a combination of diol components. With chlorohydroquinone (ClHQ) or bis(4‐hydroxyphenyl)sulfone (BPS) having a polar chlorine or sulfonyl substituent, the reaction proceeded most satisfactorily at IPA/TPA = 30/70, whereas it was IPA/TPA = 50/50 for the reaction with nonpolar methyl substituted methylhydroquinone (MeHQ). The reaction with 2,2‐bis(3,5‐dichloro‐4‐hydroxyphenyl)propane (TC‐BPA), despite having polar chlorine substituents in TC‐BPA, was not affected by IPA/TPA compositions. Alternatively, from the viewpoint of the compositions of diol components, the reactions containing 30–50 mol % of HQs or BPS yielded better results except for the reaction of IPA/TPA = 70/30, in which higher contents of MeHQ was more favorable. On the basis of sequence distributions of diol components in the resultant copolymers determined by NMR, compositions of IPA/TPA or diol components and combinations of the diols producing random copolymers yielded better results in copolycondensation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1100–1106, 2004     

Preparation of copolyesters from diols and bisphenols by the solution polycondensation with TsCl/DMF/Py as a condensing agent

A novel synthetic method for the preparation of copolyesters comprised of diols and bisphenols using tosyl chloride (TsCl)/DMF/pyridine (Py) as a condensing agent has been developed. A variety of combinations of monomers could produce relatively high molecular weight copolymers, and better results were obtained by initial oligomerization of diols followed by bisphenols. In order to demonstrate usefulness of this method, copolymers comprised of IPA/TPA (50/50), bis(2‐hydroxyethyl)terephthalate (BHET),and several bisphenols were prepared and compared to the poly(ethylene terephthalate) (PET) modified by TPA and 2,2‐bis(4‐hydroxyphenyl)propane (BPA) diacetate in terms of their thermal properties. The length of mesogenic unit segments in the thermotropic IPA/TPA (50/50)‐BHET/ 4,4′‐dihydroxybenzophenone (4,4′‐DHBP) (50/50) copolymer was changed by initial reaction of BHET followed by dropwise addition of 4,4′‐DHBP in the two‐stage polycondensation and also by varying the amounts of BHET used at the initial and final stages in the three‐stage copolycondensation, and the results were studied by NMR and their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1270–1276, 2000     

Two‐stage copolycondensation of preformed oligomers with bisphenols by tosyl chloride/dimethylformamide/pyridine from distributions of resulting oligomers determined by a combination of gel permeation chromatography and NMR

A two‐stage co‐oligomerization of the oligomers initially formed from an equimolar mixture of isophthalic acid (IPA) and terephthalic acid (TPA) and 2,2‐bis(4‐hydroxyphenyl)propane (BPA, 50 mol %) with bisphenols (BPs, 20 mol %) was carried out using a tosyl chloride/dimethylformamide/pyridine condensing agent. The distributions of the resulting oligomers (n_x‐mers), which were quenched with methanol, were determined by a combination of gel permeation chromatography (GPC) and NMR. These distributions (presented by molar percentage) were conveniently calculated with the equation n_x (mol %) = n_x (% mol by GPC) × n₀ (mol % by NMR)/n₀ (% mol by GPC), where n_x (% mol) = n_x (wt % by GPC)/its molecular weight. The results showed the distributions of the preformed IPA/TPA‐BPA oligomers to be in fairly good accord with those obtained directly from GPC and to be supported by the NMR results. The calculation was applied to the co‐oligomers prepared up to a reaction of 0.7, at which there was an increase in the number of higher oligomers indivisible by GPC and the distributions could no longer be determined by molar percentage. The calculated distributions are discussed in relation to the results of copolycondensation. The sequence distributions in the resulting co‐oligomers, which were also examined by NMR, are compared with those in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 44–51, 2004     

Copolycondensation of various compositions of isophthalic acid and terephthalic acid with hydroquinones or bisphenols by tosyl chloride/dimethylformamide/pyridine

The polycondensation of isophthalic acid (IPA)/terephthalic acid (TPA) with aromatic diols by tosyl chloride/dimethylformamide/pyridine in solution was examined through changes in the IPA/TPA compositions, the kinds of dihydroxyl components, the periods of their addition, and the reaction temperatures. The reaction proceeded favorably at IPA/TPA ratios of 70/30 to 50/50, similarly to an earlier report on the interfacial reaction. The effects of the compositions were significant in the reactions with monosubstituted hydroquinones. The results were examined from distributions of the resulting oligomers prepared at a reaction extent of 0.7, determined by gel permeation chromatography. The reaction producing better results exhibited distributions closer to the theoretical ones. The period of addition also favorably affected the distributions as well as the results of the polycondensation. These results were attributed to the change in the reaction method, in which the diols reacted with the aggregates that formed from the activated IPA and TPA. The change was likely caused by the degree of association of IPA and TPA in the aggregates, on the basis of melting points and IR spectra of mixtures of dimethyl esters of IPA and TPA prepared by the quenching of the aggregates with methanol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2321–2328, 2004     

Thermotropic copolyesters prepared by solution polycondensation with TsCl/DMF/pyridine condensing agent

When mixtures of terephthalic acid (TPA) and 1,6-naphthalenedicarboxylic acid (NDC) or 4,4′-dicarboxydiphenylether (DCDPE), TPA, and isophthalic acid (IPA) were reacted in pyridine (Py) with Tosyl chloride (TsCl)/DMF/Py to activate the diacids, the reaction mixture was soluble in Py, despite each of the separately activated diacids being insoluble. The solubility of the activated diacids was examined at a variety of acid compositions and temperatures. It was expected that a competitive reaction among the diacids with an aromatic diol in solution might be different from those in the melt, resulting in a different distribution of the acids in the copolymers. The TPA/NDC-phenylhydroquinone and DCDPE/TPA/IPA-chlorohydroquinone copolymers were prepared in solution using TsCl/DMF/Py as the condensing agent and the transition temperatures of these liquid crystalline copolyesters were compared to those obtained by melt copolycondensation. A practical depression of the transition temperature by the solution polycondensation was observed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3710–3714, 1999     

Copolycondensations of bisphenols with aggregates of isophthalic acid and terephthalic acid activated by tosyl chloride/dimethylformamide/pyridine in different manners

A mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activated by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to different structures of the aggregates of the activated IPA and TPA at the same composition of the diacids. The structures of the aggregates were evaluated on the basis of melting points and the IR spectra of a mixture of dimethyl esters of IPA and TPA produced by the quenching of the reaction mixtures with methanol. The mixture obtained by two‐step activation showed lower melting points and spectral changes due to enhanced associations of the esters with respect to the mixture prepared by the activation of them all at once. The aggregates were also examined in terms of the distributions of IPA and TPA in thermotropic copolyesters prepared from methylhydroquinone and chlorohydroquinone by their transition temperatures and ¹³C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3884–3892, 2001     

Synthesis and characterization of block poly(ester‐ether‐urethane)s from bacterial poly(3‐hydroxybutyrate) oligomers

Telechelic hydroxylated poly(3‐hydroxybutyrate) (PHB‐diol) oligomers have been successfully synthesized in 90–95% yield from high molar mass PHB by tin‐catalyzed alcoholysis with different diols (mainly 1,4‐butanediol) in diglyme. The PHB‐diol oligomers structure was studied by nuclear magnetic resonance, Fourier transformed infrared spectroscopy MALDI‐ToF MS, and size exclusion chromatography, whereas their crystalline structures, thermal properties and thermal stability were analyzed by wide angle X‐ray scattering, DSC, and thermogravimetric analyses. The kinetic of the alcoholysis was studied and the influence of (i) the catalyst amount, (ii) the diol amount, (iii) the reaction temperature, and (iv) the diol chain length on the molar mass was discussed. The influence of the PHB‐diol molar mass on the thermal stability, the thermal properties and optical properties was investigated. Then, tin‐catalyzed poly(ester‐ether‐urethane)s (PEEU) of M_n = 15,000–20,000 g/mol were synthesized in 1,2‐dichloroethane from PHB‐diol oligomers (P_ester) with modified 4,4'‐MDI and different polyether‐diols (P_ether) (PEG‐2000, PEG‐4000, and PPG‐PEG‐PPG). The influence of the PHB‐diol chain length, the P_ether/P_ester ratio, the polyether segment nature and the PEG chain length on the thermal properties and crystalline structures of PEEUs was particularly discussed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1949–1961     

Kinetics study of imidazole-cured epoxy-phenol resins

The reaction kinetics of diglycidyl ether of bisphenol A (DGEBA) cured with different concentrations of imidazole and bisphenol A (BPA) were investigated by using differential scanning calorimetry. Both dynamic and isothermal DSC were studied. Two initiation mechanisms were found to play roles in the curing reactions. One was based on adduct formation of epoxy groups with pyridine-type nitrogen and the other was based on ionic complexes of imidazole and BPA. The subsequent propagation was composed of three main reactions, viz. the epoxide/phenol reaction, the acid/base reaction, and the epoxide/R-O⁻ reaction. A generalized kinetics model was developed and used to predict the conversion of epoxide groups using a wide range of imidazole and BPA concentrations, and cure temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3233–3242, 1999     

Effect of association of dicarboxylic acids activated by TsCl/DMF/pyridine upon the copolycondensation with bisphenols

When a mixture of terephthalic acid (TPA) and various dicarboxylic acids was activated by tosyl chloride (TsCl)/dimethyl‐ formamide (DMF)/pyridine (Py), the resulting mixture became dissolved in Py, although the activated TPA was insoluble even at 120 °C. The temperature at which the mixture became soluble was varied with their compositions and the structure of diacids. Mixing the separately activated TPA and isophthalic acid (IPA) also improved the solubility of the activated TPA to some extent. The interesting phenomena were attributed to associations of the activated diacids through the dipole–dipole interactions between the carbonyl groups. The structures of associates were estimated in terms of transition temperatures of the thermotropic IPA/TPA‐methylhydroquinone and IPA/TPA‐chlorohydroquinone copolymers. The transition temperatures were significantly affected by the temperature of polycondensation, the preparative procedures of a mixture of the activated diacids, and several additives. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 196–201, 2001     

Comparison of the catalytic activity of PHB–depolymerase,yeast lipase,and papain on poly(ethylene adipate), poly(ethylene succinate), and poly (3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)

PHB-depolymerase degraded poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] (PHB/V) significantly. No other enzyme used in this study showed activity toward PHB/V. Weight loss and gel permeation chromatography (GPC) studies suggested that enzymatic degradation takes place by a surface erosion mechanism. pH studies demonstrated that enzymatic degradation occurs even when little weight loss is observed. Differential scanning calorimetry (DSC) analysis demonstrated that the enzymes studied prefer to degrade amorphous regions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2581–2585, 1999     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

Synthesis and characterization of polycyclic structures and linear polycarbonate copolymers from a bisphenol A dimer

An o,o′‐methylene‐bridged bisphenol A (BPA) dimer 2 was synthesized by a one‐step reaction between formalin and excess BPA in the presence of a cation exchange resin in a polar aprotic solvent. Novel oligomeric polycyclic structures were synthesized by the reaction of reactive difunctional halides, methyl phosphonic dichloride, phenyl phosphonic dichloride, and dimethyl dichlorosilane with the BPA dimer under high‐dilution conditions. The yields of the polycyclics were quite high. NMR and matrix‐assisted laser desorption ionization–time of flight mass spectrometry (MALDI–TOF MS) were very useful in the characterization of the dimer and its oligomeric polycyclic analogs. These polycyclics can potentially be used as precursors for advanced thermosetting materials. A series of polycarbonate copolymers of BPA were synthesized by solution polycondensation of the methylene bridged dimer of BPA with triphosgene. Alternatively, the co‐polycarbonate containing crosslinkable moieties was synthesized by in‐situ polymerization of BPA and BPA dimer with triphosgene. The copolymers were characterized by GPC. TG/DTA and DSC were used to investigate the thermal properties of the co‐polycarbonates. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 927–935, 1999     

Thermal and dielectric properties of oriented liquid crystalline polysiloxane doped with azo‐dye

Investigations of dielectric relaxation and thermal properties of mixtures composed of liquid crystalline side‐chain polysiloxane and low molecular mass azo‐dye have been carried out. The dyes have been chosen to solublize well in the polymer matrix at concentrations up to 0.08 mol fraction. The dielectric relaxation experiments have shown the presence of separate processes attributed to reorientational motions of mesogenic side groups and dye molecules. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 369–377, 1999     

液晶嵌段共聚物PET/60PHB-b-PC的合成及结构与性能

采用ＰＥＴ齐聚物的原位乙酰化法通过加入少量乙二醇（ＥＧ）合成了端羟基液晶聚合物ＰＥＴ／６０ＰＨＢ，并将其作为大单体，与双酚Ａ及碳酸二苯酯通过熔融酯交换法，进一步制得了液晶嵌段共聚物ＰＥＴ／６０ＰＨＢ ｂ ＰＣ．研究了合成规律，并借助粘度测定、ＤＳＣ、偏光显微镜、Ｘ 光衍射和红外光谱分析等手段对合成的液晶嵌段共聚物进行了表征．研究表明，当ＰＥＴ齐聚物的ηｉｎｈ＝００５～００７ｄＬ／ｇ，Ａｃ２Ｏ／ＰＨＢ（ｍｏｌ／ｍｏｌ）＝１３，ＥＧ／ＰＥＴ（ｍｏｌ／ｍｏｌ）＝００６时能获得颜色、液晶性、溶解性均很好的端羟基液晶聚合物ＰＥＴ／６０ＰＨＢ，以此液晶聚合物为原料，采用合适的配方与工艺，能获得粘度较高、液晶性较好，并且熔体流动性很好的液晶嵌段共聚物ＰＥＴ／６０ＰＨＢ ｂ ＰＣ．通过偏光显微镜与Ｘ 光衍射观察，证明此嵌段共聚物呈现向列型液晶织构，但其液晶态织构与纯ＰＥＴ／６０ＰＨＢ、ＰＥＴ／６０ＰＨＢ和ＰＣ的混合物明显不同．此外，还初步建立了用红外的分析手段鉴定液晶聚合物ＰＥＴ／６０ＰＨＢ端基的方法．     

Crystallization and melting behavior of the soft and hard segments in poly(ester-ether)s. I. Ethylene oxide-ethylene terephthalate segmented copolymers

The crystallization and melting behavior of a series of ethylene oxide-ethylene terephthalate (EOET) segmented copolymers with different soft segment molecular weight and hard segment weight content were studied by differential scanning calorimeter (DSC) and polarized microscope. The crystallizability of both the hard and the soft segments became worse than that of the corresponding homopolymers due to the interactions of the different segments. The crystallizability of the soft segments is mainly determined by the soft segment molecular weight, but is affected greatly by the content and the crystallinity of the hard segments. Conversely, the soft segment length and content also have a great effect on the crystallization of the hard segments. However, the melting points of the hard segments are determined by the average hard segment length. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2918–2927, 1999     

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate)–Poly(vinyl‐acetate) blends

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate) (PHB)–poly(vinyl acetate) (PVAc) blends from the melt were investigated by differential scanning calorimetry using various cooling rates. The results show that crystallization of PHB from the melt in the PHB–PVAc blends depends greatly upon cooling rates and blend compositions. For a given composition, the crystallization process begins at higher temperatures when slower scanning rates are used. At a given cooling rate, the presence of PVAc reduces the overall PHB crystallization rate. The Avrami analysis modified by Jeziorny and a new method were used to describe the nonisothermal crystallization process of PHB–PVAc blends very well. The double‐melting phenomenon is found to be caused by crystallization during heating in DSC. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 443–450, 1999     

Molecular engineering of photoactive liquid crystalline polyester epoxies containing benzylidene moiety

A series of photoactive liquid crystalline polyester epoxies incorporating bisbenzylidene segments as photoactive mesogenic cores were synthesized by polyaddition of diepoxy monomers and terephthalic acid/trimesic acid. To investigate the influence of structural parameters such as, molecular architecture, structural rigidity of mesogenic unit and substituents on thermal, mesogenic, and photoactive properties, the bisbenzylidene segment was incorporated into one acyclic and two cycloalkanone units with two and four substituents, respectively in both linear and hyperbranched architectures. Degree of branching of hyperbranched polymers was found to be in the range of 0.49–0.62. All polymers exhibited nematic mesophase (nematic droplets). Photo induced (2π + 2π) cycloaddition reaction, upon exposure to light at 365 nm, was examined. Inter molecular photocycloaddition was confirmed by photoviscosity measurement of UV irradiated polymer solutions. Faster photo induced reactivity of polymers in hyperbranched architecture was observed when compared to linear structure. Acyclic units facilitated photocycloaddition, and five‐membered ring showed higher photoactivity compared to six‐membered ring. The steric hindrance caused by substituents decreased the photoactivity of polymers. Refractive index change was found to be in the range of 0.015–0.024. Substantial variation of refractive index indicates that these polymers could be used for optical recording. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7637–7655, 2008     

Solution polycondensation of isophthalic acid/terephthalic acid and tetrachlorobisphenol A of low polymerizability with tosyl chloride/dimethylformamide/pyridine improved by the introduction of comonomers of smaller sizes

The copolycondensations of a mixture of equal parts of isophthalic acid and terephthalic acid with tetrachlorobisphenol A (TC‐BPA) and various aromatic diol comonomers were performed with a tosyl chloride/dimethylformamide/pyridine condensing agent. The reaction with bisphenols containing nonpolar substituents yielded better results than the reaction with polar groups did. Dihydroxybenzenes smaller in size than bisphenols of two benzene rings, especially chlorohydroquinone and chlororesorcinol, were satisfactorily incorporated and yielded copolymers of high inherent viscosities and weight‐average molecular weights (by gel permeation chromatography). The results of the copolycondensations were examined with sequence distributions in the resultant copolymers by NMR and were well evaluated by the ratio of the length of comonomer unit segments to TC‐BPA unit segments. Homopolycondensation with TC‐BPA in the presence of dichlorobenzenes as additives was also promoted to some extent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 821–830, 2003     

Synthesis and characterization of side-chain liquid-crystalline poly(ether ester)s having p-substituted biphenyl mesogenic side groups

Several novel mesogenic spiro-orthoester monomers such as 1,6,10-trioxaspiro[4,5]decanes 4 , containing biphenyl mesogens at the C-8 positions of the five- and six-membered spirocyclic ring, through the alkylene spacers of different lengths were prepared by condensation reaction of the corresponding biphenyl mesogenic 1,3-propanediol 3 with 2,2-diethoxytetrahydrofuran, with 50–75% yields. Through cationic double ring-opening polymerization, carried out with boron trifluoride etherate as an initiator (5 mol % vs. monomer) in bulk at 150°C, spiro-orthoester monomers 4 afforded a novel class of side-chain thermotropic LC polymers with a poly(ether ester) as the main chain 8 . The liquid-crystalline properties of the spiro-orthoester monomers and the resulting polymers were examined by differential scanning calorimetry and optical polarized microscopy. Biphase separation was observed in the side-chain liquid-crystalline poly(ether ester)s upon annealing in the broad isotropic region. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2439–2455, 1998     

Uracil as Nucleating Agent for Bacterial Poly[(3‐Hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)] Copolymers

In this study, uracil has been introduced as the nucleating agent (NA) for bacterially synthesized poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)] (PHBHHx) copolymers with HHx content of 5, 10, 18 mol‐%, and poly(3‐hydroxybutyrate) (PHB) homopolymer for the first time. Its effect was compared with the conventional NA of PHB, that is, boron nitride (BN), and two other naturally occurring pyrimidine derivatives, i.e., thymine and cytosine. The effects of uracil on the crystallization kinetics, melting behavior, spherulite morphology, and crystalline structure of PHBHHx and PHB were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide‐angle X‐ray diffraction (WAXD). Uracil and BN exhibit the comparable nucleation efficiency on the crystallization of PHB, whereas uracil shows much more effective nucleation ability than BN for PHBHHx copolymers. With incorporation of 1 wt.‐% uracil, PHBHHx with 0–10 mol‐% HHx units can finish crystallization upon cooling at 10 °C · min^?1. The crystallization half‐times (t_1/2) of all the PHB and PHBHHx samples decrease significantly with presence of uracil. The crystallization rate of polymers further enhances with increase in uracil concentration. With addition of 1 wt.‐% uracil, the t_1/2 value of PHBHHx with 10 mol‐% HHx units melt‐crystallizing at 80 °C decreases to ≈4.0% of the neat polymer, and the nucleation density increases by 3–4 orders of magnitude. The incorporation of uracil has no discernable effect on the crystalline structure of PHBHHx, as evidenced by WAXD results. It was proposed that the nucleation mechanism of the uracil/PHBHHx (or PHB) system might be the epitaxial nucleation.