Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

The structure and properties of ultrahigh molecular weight polycarbonate synthesized by solid‐state polymerization in micro‐layers (SSP_m) are reported. A low molecular weight prepolymer derived from the melt transesterification of bisphenol A and diphenyl carbonate as a starting material was polymerized to highly amorphous and transparent polycarbonate of molecular weight larger than 300,000 g mol^?1 in the micro‐layers of thickness from 50 nm to 20 µm. It was observed that when the polymerization time in micro‐layers was extended beyond conventional reaction time, insoluble polymer fraction increased up to 95%. Through the analysis of both soluble and insoluble polymer fractions of the high molecular weight polycarbonate by ¹H NMR spectroscopy and pyrolysis‐gas chromatography mass spectrometry (Py‐GC/MS), branches and partially crosslinked structures have been identified. The thermal, mechanical and rheological properties of the ultra‐high molecular weight nonlinear polycarbonates synthesized in this study have been measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and rheometry. The nonlinear chain structures of the polymer have been found to affect the polymer's thermal stability, mechanical strength, shear thinning effect, and elastic properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41609.     

Solid‐state polymerization of bisphenol A polycarbonate with a spray‐crystallizing method

A novel crystallization method for the production of high‐molecular‐weight bisphenol A polycarbonate by solid‐state polymerization is suggested. In this method, a low‐molecular‐weight polycarbonate prepolymer is dissolved in a solvent and then partially crystallized with a novel spray‐crystallizing method to prepare crystallized polycarbonate particles having a very uniform and porous structure with a narrow melting region. As a result, during solid‐state polymerization, the phenol byproduct can be easily removed from the polymerizing porous polycarbonate particles, and the polymerization rate is dramatically increased. In particular, the effects of the crystallization methods on secondary crystallization during solid‐state polymerization and the melting behavior have been investigated with differential scanning calorimetry studies. The final product, a high‐molecular‐weight polycarbonate, displays a very narrow molecular weight distribution and uniform physical properties. A simultaneous process and an adequate reactor design for spray crystallization and solid‐state polymerization are also suggested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The stabilization of bisphenol‐A based polycarbonate by phosphine oxide

A Bisphenol‐A based polycarbonate was stabilized by a new polymer stabilizer named di(p‐butoxyphenyl)cyclohexylphosphine oxide. The stabilizer was mixed with the polymer in methylene chloride solution. Later, the solution was vaporized and the stabilized polymer was dried. Specimens were cut and heat treated at different temperature and durations. Small amounts of stabilizer enhanced the breaking strength and elongation at break properties of as molded and heat treated polycarbonate. The modulus of elasticity reduced with stabilization. The stabilizer had a plasticizing effect too. At high stabilizer rates (c > 1%) both thermal and mechanical properties were deteriorated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solvent‐induced crystallization of a polycarbonate surface and texture copying by polydimethylsiloxane for improved surface hydrophobicity

The influence of the immersion period on the crystallization of polycarbonate (PC) was investigated, and the resulting texture configurations of the crystal structures were reconstructed with polydimethylsiloxane (PDMS). Analytical tools, including optical microscopy, scanning electron microscopy, atomic force microscopy, X‐ray diffraction, the sessile drop technique, Fourier transform infrared spectroscopy, microtribometry, and ultraviolet–visible spectrophotometry, were used to characterize crystallized PC and PDMS surfaces. We found that the crystallized PC surface possessed microsize/nanosize spherulites, voids, and fibrils, and the increasing immersion period increased the texture height and spherulite concentration at the surface. The residual stress in the crystallized PC wafer was compressive, and it was on the order of ?30 MPa. The friction coefficient of the crystallized PC surface remained lower than that of the as‐received PC wafer, and the increase in the immersion period lowered the friction coefficient. The crystallized PC surface demonstrated superhydrophobic characteristics, and the maximum contact angle occurred with 6 min of immersion. The PDMS exactly reconstructed the texture of the crystallized PC surface, except those of the nanofibrils and subnanofibrils. The droplet contact angle attained a higher values for the PDMS replicated surfaces than for those corresponding to the crystallized PC wafer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43467.     

Vapor‐induced crystallization behavior of bisphenol‐A polycarbonate

The effects of exposure time and vapor pressure on the crystallization behaviors of bisphenol‐A polycarbonate (BAPC) films were investigated at 25°C by using differential scanning calorimetry (DSC). Double melting peaks were observed for various BAPC samples after vapor‐induced crystallization. The low temperature melting peak shifted to higher temperature and became sharper with increasing exposure time, and could be assigned to defective crystals with smaller crystal size. Crystallinity and average crystal dimension normal to (020) were calculated from wide‐angle X‐ray diffraction spectra. A good agreement was obtained between crystallinity values obtained from WAXD and those from DSC. The morphology of crystallized samples after various exposure time periods was examined by means of polarized optical microscopy. Nucleation occurred at the initial stage of vapor‐induced crystallization. Poor crystals become perfect through segment reorganization with increasing exposure time, and spherulites' growth was observed. The average diameter of spherulites increased from 2 μm for 1 h, to 7 and 16 μm after 3 and 56 h, respectively. POLYM. ENG. SCI., 46:729–734, 2006. © 2006 Society of Plastics Engineers     

Surface and wetting characteristics of textured bisphenol‐A based polycarbonate surfaces: Acetone‐induced crystallization texturing methods

Polycarbonate (PC) sheet is a promising material for facile patterning to induce hydrophobic self‐cleaning and dust repelling properties for photovoltaic panels’ protection. An investigation to texture PC sheet surfaces to develop a self‐cleaning structure using solvent induced‐crystallization is carried out using acetone. Acetone is applied in both liquid and vapor states to generate a hierarchically structured surface that would improve its contacts angle and therefore improve hydrophobicity. The surface texture is investigated and characterized using atomic force microscopy, contact angle technique (Goniometer), optical microscopy, ultraviolet‐visible spectroscopy (UV–vis) and Fourier transform infrared spectroscopy. The findings revealed that the liquid acetone‐induced crystallization of PC surface leads to a hierarchal and hydrophobic surface with an average contact angle of 135° and average transmittance <2%. However, the acetone vapor induced‐crystallization results in a slightly hydrophilic hierarchal textured surface with high transmittance; in which case, average contact angle of 89° and average transmittance of 69% are achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43074.     

Morphology development and crystallization behavior of a poly(ethylene terephthalate)/polycarbonate blend

The morphology development and crystallization behavior of an extruded poly(ethylene terephthalate)/polycarbonate blend were studied with optical microscopy, light scattering, and differential scanning calorimetry (DSC). During annealing at 280°C, liquid–liquid phase separation via spinodal decomposition proceeded in a melt‐extruded specimen. After the formation of the domain structure, the blend slowly underwent phase homogenization by transesterification between the two polymers. The specimen, annealed for various times (t_s's) at 280°C, was subjected to a temperature drop to 180°C for the isothermal crystallization, and then the effects of liquid‐phase changes on crystallization were investigated. The crystal growth rate decreased with t_s. The slow crystallization with a large t_s value was associated with the composition change of the separated phases and the change of the sequence distribution in the polymer chains during annealing. The influence of t_s on the endothermic behavior of the samples was examined. As t_s increased, the recrystallization rate was retarded during the DSC scan, displaying multiendothermic behavior. The DSC data also suggested that the increased level of transesterification would give rise to a higher number of species being rejected from the primary crystals, leading to enhanced secondary crystallization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Heterogeneous palladium–cobalt bimetal catalyst for the oxidative carbonylation of bisphenol A to polycarbonate

Polycarbonates (PCs) were prepared by the oxidative carbonylation of bisphenol A and carbon monoxide with a hydrotalcite‐supported Pd–Co complex, a Pd–Co–poly(4‐vinylpyridine) complex [Pd–Co–(p‐4vpy)], a Pd–Co–polystyrene‐supported triphenylphosphine complex (Pd–Co–PS‐TPP), or a Pd–Co–polyvinylpyrrolidone complex (Pd–Co–pvp) as a heterogeneous Pd–Co bimetal catalyst to separate the PC solution and the Pd–Co bimetal catalyst after the reaction. Propylene carbonate was used as a halogen‐free solvent. Pd–Co–(p‐4vpy) and Pd–Co–PS‐TPP showed recycling potential, whereas Pd–Co–pvp, though not having recycling potential, yielded a high turnover number with a maximum of 1462. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The rate acceleration in solid‐state polycondensation of PET by nanomaterials

The effect of nanomaterials on the solid‐state polycondensation (SSP) of PET was investigated using intrinsic viscosity measurement, wide‐angle X‐ray diffraction, differential scanning calorimetry, and polarizing microscope. The results showed that the montmorillonite nanomaterials could greatly increase the rate of solid‐state polycondensation of PET, probably due to the nucleation of montmorillonite nanomaterials for PET crystallization, which resulted in lower crystallinity, more small crystals, and more surfaces of the crystals. The surfaces of microcrystal and richer amorphous regions benefitted the polycondensation reaction of PET and diffusion of volatile by‐products, which led to the higher rate of SSP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 971–976, 2004     

Heterogeneous Pd catalyst for oxidative carbonylation of bisphenol A to polycarbonate

Polycarbonates (PCs) were prepared by oxidative carbonylation of bisphenol A and carbon monoxide, using a Pd‐polybipylidyl complex, Pd‐polyvinylpyridine complex, smectite‐supported Pd complex, or hydrotalcite‐supported Pd complex as a heterogeneous Pd catalyst to separate the PC solution and the Pd catalyst after the reaction. Propylene carbonate was used as a halogen‐free solvent. When Co(OAc)₂·4H₂O was used as the inorgano‐redox catalyst, all of the Pd compounds gave a good PC yield with the recycling potential of the catalyst. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Aliphatic–aromatic poly(butylene carbonate‐co‐terephthalate) random copolymers: Synthesis,cocrystallization, and composition‐dependent properties

A series of aliphatic–aromatic poly(carbonate‐co‐ester)s poly(butylene carbonate‐co‐terephthalate)s (PBCTs), with weight‐average molecular weight of 113,000 to 146,000 g/mol, were synthesized from dimethyl carbonate, dimethyl terephthalate, and 1,4‐butanediol via a two‐step polycondensation process using tetrabutyl titanate as the catalyst. The PBCTs, being statistically random copolymers, show a single T_g over the entire composition range. The thermal stability of PBCTs strongly depends on the molar composition. Melting temperatures vary from 113 to 213°C for copolymers with butylene terephthalate (BT) unit content higher than 40 mol %. The copolymers have a eutectic melting point when about 10 mol % BT units are included. Crystal lattice structure shifts from the poly(butylene carbonate) to the poly(butylene terephthalate) type crystal phase with increasing BT unit content. DSC and WAXD results indicate that the PBCT copolymers show isodimorphic cocrystallization. The tensile modulus and strength decrease first and then increase according to copolymer composition. The enzymatic degradation of the PBCT copolymers was also studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41952.     

Synthesis of linear aliphatic polycarbonate macroglycols using dimethylcarbonate

A series of linear aliphatic polycarbonate polyols were synthesized using dimethylcarbonate and a linear alkane diol or specific combinations of linear alkane diols. Polyol synthesis was carried out in a two‐stage process using dimethylcarbonate and a linear alkane diol to prepare a series of homopolymer polycarbonate polyols. Polyol grades were characterized using Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetery techniques. Suitable reaction conditions were developed to yield polycarbonate polyols of number average molecular weight between 700 and 1700. The crystallinity of the polycarbonate polyols was shown to reduce as the molecular weight of the alkane diols used in the polycarbonate synthesis was increased. These polymers offer the potential for use in the synthesis of ether free polyurethane elastomers for biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Homogeneous palladium catalyst for the oxidative carbonylation of bisphenol A to polycarbonate in propylene carbonate

Polycarbonates (PCs) were prepared in a propylene carbonate solvent by the oxidative carbonylation of bisphenol A with Pd/bithienyl complexes, Pd/bipyridyl complexes, and Pd C σ-bonded complexes for comparison as homogeneous Pd catalysts. With the Pd/bipyridyl complexes, the 6,6′-disubstituted 2,2′-bipyridyl ligand showed a stronger substituent effect than the 2,2′-bipyridyl ligand, which lacked substituents at the 6,6′ positions. With the Pd/bithienyl complexes, however, the substituent effect was not seen. The Pd/bithienyl complexes, which lacked substituents at the 5,5′ positions, gave a PC yield that was the same as the yield of those that had substituents at the 5,5′ positions. The combination of the Pd C σ-bonded complexes and an inorganoredox cocatalyst showed a PC polymerization behavior that was different from the other two types of complexes. When Co(OAc)₂·4H₂O was used as the inorganoredox cocatalyst, all of the Pd C σ-bonded complexes gave a good PC yield. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Small‐molecule‐induced miscibility of isosorbide‐based polycarbonate with bisphenol A polycarbonate

In this study, we investigated the influence of the small molecule 4,4′‐thiobis(6‐tert‐butyl‐m‐methyl phenol) (AO300) on the miscibility of poly(isosorbide‐co‐1,4‐cyclohexanedimethanol carbonate) (IcC–PC) with bisphenol A polycarbonate (BPA–PC) through the formation of hydrogen‐bonding networks. Differential scanning calorimetry and morphological observation revealed that the initially, immiscible BPA–PC/IcC–PC blends become miscible through the addition of small molecules. Fourier transform infrared spectroscopy confirmed that intermolecular hydrogen bonds formed between the hydroxyl groups of AO300 and the carbonyl groups of the studied polycarbonates. These polycarbonates exhibited different hydrogen‐bonding behaviors and various degrees of glass‐transition temperature composition dependence. Dynamic mechanical analysis demonstrated that AO300 played an antiplasticization role in the BPA–PC/IcC–PC blends with improved storage moduli. To our knowledge, this article is the first to describe the miscibility of isosorbide‐based polycarbonate with BPA–PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44537.     

Crystallization and solid‐state polymerization of poly(aryl ester)s

The crystallization and solid‐state polymerization (SSP) of poly(aryl ester)s was investigated. Oligomers with different end‐groups were prepared by degradation of commercially available poly(aryl ester)s. The SSP of these oligomers was carried out after crystallization and under reduced pressure, in the presence of various catalysts. Polymers were characterized by means of their inherent viscosities and thermal properties. It has been found that Ti(OⁱPr)₄ was a better catalyst for SSP. The structures and morphologies of semicrystalline poly(aryl ester)s were investigated by X‐ray diffraction and differential scanning calorimetry (DSC). Copyright © 2004 Society of Chemical Industry     

Effects of crystallinity on solid‐state polymerization of poly(ethylene terephthalate)

There has been a widely held assumption that the solid‐state polymerization (SSP) rate of poly(ethylene terephthalate) (PET) decreases with increasing crystallinity. Several published articles that purported to prove this assumption were based on faulty experiments. Therefore, a proper experimental procedure has been used to study the true effects of crystallinity on the SSP of PET. The results show that, for PET in pellet and powder forms, the SSP rate increases with increasing crystallinity. This is because an increase in the crystallinity results in increased end‐group concentration in the amorphous phase, where SSP reactions take place, and decreased concentrations of inactive end groups trapped inside the crystals, thereby increasing the rates of end‐group collision and reactions. These positive effects outweigh the negative effect of the increased byproduct‐diffusion resistance because of the increase in crystallinity. As the particle size of PET is increased beyond a critical value of about 7 mm, the SSP rate actually decreases with increasing crystallinity because of the excessively increased byproduct‐diffusion resistance within the PET particles. However, this critical particle size is far greater than the pellet sizes of commercial PET resins. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 623–632, 2006     

Structure development during crystallization and solid‐state processing of poly(glycolic acid)

DSC and time‐resolved WAXS and SAXS are used to study the structure development during isothermal crystallization of poly(glycolic acid) (PGA) in the temperature range 180–195°C. It is shown that the crystallization rate increases with degree of supercooling in the temperature range of consideration. WAXS and DSC crystallinity measurements agree well and a final crystallinity of 50% is found independently of the crystallization temperature. In‐situ SAXS measurements indicate that for PGA the final crystal thickness approaches a limiting value of 70 Å independent of the crystallization temperature in the range 195–180°C. The material develops a well‐defined lamellar structure during crystallization at the highest crystallization temperature under study (195°C). We show that by increasing the degree of supercooling it is possible to hinder the formation of the lamellar structure and crystals, resulting in a less ordered structure. We report that PGA fibers with elastic modulus in the range 20–25 GPa can be prepared by adequate control of the structure before solid‐state plastic deformation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Unique pressure‐crystallized structures in ternary bisphenol‐a polycarbonate/dioctyl phthalate/fullerene C60 composites

We report pressure‐controlled fast growth of unique crystalline structures of bisphenol‐A polycarbonate (PC) was achieved by the introduction of both dioctyl phthalate (DOP) and fullerene C60. PC/DOP/C60 ternary composites with an overall good C60 dispersion were prepared by an easy physical and mechanical route, and then crystallized in a piston‐cylinder high‐pressure apparatus by varying temperature, pressure, crystallization time and composite composition. The crystallization of PC was greatly hastened by the blending with DOP and C60, and its melting point was increased to 288.25 degrees centigrade by the subsequent high‐pressure treatment, which was around 40° centigrade higher than that of the samples crystallized at normal pressure. Three‐dimensional spiky crystalline spheres were formed with the increase of crystallization temperature, which began with zero‐dimensional nanogranules, and then developed by merging process through the stages of one‐dimensional lamellar crystallites and two‐dimensional dendrites. With pressure increased, the granules merged first into plate crystals, and then into micro‐spheres with rugged surfaces or porous structures. Also, sometimes the granules organized into rugged crystalline nanoballs, and peony‐like stereo‐open structures were observed by changing composite composition. The as‐prepared three‐dimensional crystalline structures, with their large specific areas, may diversify niche functional applications as surface active materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chopping high‐molecular weight poly(1,4‐butylene carbonate‐co‐aromatic ester)s for macropolyol synthesis

The condensation of a mixture of dimethyl carbonate and phthalate derivatives with 1,4‐butanediol (BD), catalyzed by sodium alkoxide, generated high‐molecular weight poly(1,4‐butylene carbonate‐co‐aromatic ester)s with molecular weights (M_n) of 50–120 kDa. The subsequent addition of polyols [BD, glycerol propoxylate, 1,1,1‐tris(hydroxymethyl)ethane, or pentaerythritol] chopped these high‐molecular weight polymers to afford macrodiols or macropolyols with facile control of their molecular weights (M_n, 2000–3000 Da) and unique chain topological compositions. Macropolyols prepared by chopping poly(1,4‐butylene carbonate‐co‐terephthalate) were waxy in nature, whereas those containing isophthalate and phthalate units were oily. The macropolyols synthesized by this chopping method may have potential applications in the polyurethane industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43754.