Crystallization and morphology of poly(ethylene succinate) and poly(β-hydroxybutyrate) blends

Summary The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy. The results indicate that PHB and PES are miscible in the melt. Consequently the blend exhibits a depression of the melting temperature of both PHB and PES. In addition, a depression of the equilibrium melting temperature of PHB is observed. The Flory-Huggins interaction parameter (χ₁₂ ), obtained from melting point depression data, is composition dependent, and its value is always negative. Isothermal crystallization in the miscible blend system PES/PHB is examined by polarized optical microscope. The presence of the PES component gives a wide variety of morphologies. The spherulites exhibit a banded structure and the band spacing decreases with increase PES content. Received: 29 June 1998/Revised version: 31 August 1998/Accepted: 10 September 1998     

Synthesis and characterization of polymers from β-propiolactone and poly(ethylene glycol)s

Uncatalysed polymerizations of β-propiolactone with low-molecular-weight poly(ethylene glycol)s were carried out in bulk, at temperatures in the range of 70 to 120°C. ¹H nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) measurements on the resulting products indicated a block copolymer structure. Gel permeation chromatography (g.p.c.) and d.s.c. analyses showed that in some cases the copolymerization is accompanied by homopolymerization of β-propiolactone, probably due to the presence of residual water in the poly(ethylene glycol). N.m.r. and infra-red (i.r.) spectra of copolymers revealed the presence of hydroxyl and carboxyl end groups. The copolymerization reaction may be visualized as a two-step process, in which the ring opening of β-propiolactone takes place on both the hydroxyl groups of poly(ethylene glycol), followed by repetitive monomer addition forming an ester-ether-ester triblock copolymer.     

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Effects of the lamination temperature on the properties of poly(ethylene terephthalate-co-isophthalate) in polyester-laminated tin-free steel can — I. Characterization of poly(ethylene terephthalate-co-isophthalate)

The effects of lamination temperature on the properties of poly(ethylene terephthalate-coisophthalate) (co-PET), such as thermal, mechanical, and barrier properties, have been investigated in co-PET laminated steel. The variation of the degree of crystallinity and the orientation of the co-PET film during the lamination process was examined using DSC, X-ray diffraction, and birefringence, and water vapor permeability was also measured with varying lamination temperature. Both the degree of crystallinity and the orientation of the co-PET film decreased and water vapor permeability increased with increasing lamination temperature. The stress-strain curves of the co-PET films were different, depending on the lamination temperature. The stress in the co-PET film laminated at higher temperature was lower at a given strain, due to the increase of the amorphous region. The effects of annealing temperature and the extent of drawing on the residual stress in co-PET/tin-free steel (TFS) joints were investigated by examining the stress relaxation behavior of co-PET. It was necessary to heat co-PET/TFS joints at more than 150°C in order to eliminate the residual stress.     

Prevention of poly(vinyl chloride) degradation through organic terephthalamides generated from poly(ethylene terephthalate) waste

The use of organic compounds as thermal stabilizers for poly(vinyl chloride) (PVC) stabilization is the current state of art worldwide owing to their high efficiency and nontoxic residues after degradation. Terephthalamide, N,N′-dimethylterephthalamide and N,N′-dibutylterephthalamide have been prepared via depolymerization of poly(ethylene terephthalate) through an economical and environmentally friendly approach. These compounds have been examined as thermal stabilizers for PVC formulations and found to exhibit high thermal stabilizing effects. Thermal stability measurements were performed using conventional Congo red test method. Color change experiments were conducted by heating the samples at 200 °C in air, and the colored compounds formed were extracted and compared with the help of UV–visible spectroscopy. Fourier transform infrared spectroscopic studies of organic terephthalamides incorporated PVC samples have been performed in order to insight the probable mechanistic aspects involved in thermal stabilization process. Thermogravimetric analysis (TGA) thermograms of PVC sheets loaded with 10 wt % organic terephthalamides have been recorded and were found stable below 200 °C. SEM and energy dispersive X-ray analysis of char residues of TGA samples were performed supporting the proposed thermal stabilizing action of the organic terephthalamides. Furthermore, specific gravity and mechanical performance of the PVC sheets have also been reported assisting in finding suitable commercial applications of PVC formulations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48022.     

Impact of organoclays on the phase morphology and the compatibilization efficiency of immiscible poly(ethylene terephthalate)/poly(ε-caprolactone) blends

Adding nanofillers Cloisite 30B (C30B) and Cloisite 15A (C15A) to poly(ethylene terephthalate) (PET)/poly(ε-caprolactone) (PCL) (70/30, wt/wt) blends via melt blending can improve their phase morphology and change their interface properties. The effects of the different selective localization of clay on the structure and the morphologies are studied and evaluated by theoretical and experimental methods. It is found that C30B is selectively localized in PET and at the PET-PCL interface, whereas C15A is mainly localized at the interface. Moreover, the changes in the rheological behavior of the blends are attributed to the formation of clay network-like structures. X-ray diffraction, scanning electron microscope, and transmission electron micrograph observations also evidenced an exfoliated and/or intercalated structure of C30B, and intercalated structure of C15A in the blend, together with significant morphology changes of the initially immiscible blend. The relative permeability to PET/PCL of the nanocomposites decreased with the increasing of nanoclays content. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48812.     

Rheological properties of poly(ε-caprolactone) and poly(styrene-co-acrylonitrile) blends

Summary Rheological properties of poly(-caprolactone) (PCL) and Poly (styrene-co-acrylonitrile) (SAN) blends were examined as a function of the acrylonitrile (AN) content in SAN, to systematically understand the correlation between the interaction parameter and the theological properties of miscible polymer blends. When the plateau modulus (G _N ⁰) and zero shear viscosity ( ₀) of the PCL/SAN blends are plotted against the AN content in SAN, a minimum is observed. Qualitatively, the results obtained parallel the variation of the interchain interaction with the AN content. The negative deviation ofG _N ⁰ and ₀ from linearity seems to be attributed to the increase in the entanglement molecular weight between dissimilar chains which results from the chain extension caused by interchain interaction.     

Synthesis and characterization of star-shaped block copolymer of poly-(?-caprolactone) and poly(ethyl ethylene phosphate) as drug carrier

A series of novel 4-arm biodegradable star block copolymers of poly(?-caprolactone) and poly(ethyl ethylene phosphate) were synthesized via ring-opening polymerization of 2-ethoxy-2-oxo-1,3,2-dioxaphospholane using hydroxyl terminated 4-arm star-shaped poly(?-caprolactone) and stannous octoate co-initiation system. Gel permeation chromatography (GPC), NMR and FT-IR were used to demonstrate the structure and analyze their compositions. The self-assembly behavior of these star-shaped copolymers in aqueous solution was studied by ¹H NMR and fluorescence technique, and the results indicated those copolymers formed nanoparticles in aqueous solution with hydrophobic poly(?-caprolactone) core and hydrophilic poly(ethyl ethylene phosphate) shell. The critical micelle concentration was relative to the length of poly(?-caprolactone) and poly(ethyl ethylene phosphate) block. Paclitaxel was encapsulated in the micelles and the release behavior demonstrated that a longer hydrophobic block resulted in slightly slower release rate from the micelles. These copolymer micelles were biocompatible and potential as drug-delivery vehicles for pharmaceutical application.     

Structure–property evolution of poly(ethylene terephthalate)/poly(trimethylene terephthalate) side-by-side self-crimp filament

To investigate the microstructure and mechanical properties of self-crimping two-component side-by-side bicomponent filament, this paper focuses on systematically investigating the structure–property evolution of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) side-by-side bicomponent filament prepared via melt spinning with various component ratios, drawing and heating treatment. The investigation was operated upon the combination of morphology analysis, thermal analysis, crystallization, and orientation analysis. The variation of cross section and curl-morphology, crystallization, and microstructures mainly containing lamellar and microfibrillar crystals as well as their effects on the mechanical and self-crimping properties were discussed. As the draft ratio (DR) increases, the crystallinity, sonic orientation factor, tensile strength, and crimp-recovery rate of the filaments were increased. The sonic orientation factor in the crystalline region decreases from 0.923 to 0.777 but increases from 0.677 to 0.903 in the amorphous region. In contrast to the variation of the DR, heating temperature has a limited effect on the tensile strength of the PET/PTT hybrid filaments. Crimp-recovery rate, however, first increases to 11.8 and then decreases to 9.8 with an increasing heating temperature from 144 to 168°C. Most of these behaviors have been attributed to changes in the ratio of contractile stress for both PTT and PET components, originating from microstructural evolution in hybrid filaments, including crystal growth, breakage, deflection, and deformation of chains along the axial direction. As a summary, an interpretive diagrammatic sketch has been proposed to clarify the structure–property relationships of the commercial PET/PTT filaments.     

Biodegradable nanoparticles of methoxy poly(ethylene glycol)-b-poly( d, l-lactide)/methoxy poly(ethylene glycol)- b-poly(ϵ-caprolactone) blends for drug delivery

The effects of blend weight ratio and polyester block length of methoxy poly(ethylene glycol)-b-poly( d, l-lactide) (MPEG- b-PDLL)/methoxy poly(ethylene glycol)- b-poly(ϵ-caprolactone) (MPEG- b-PCL) blends on nanoparticle characteristics and drug release behaviors were evaluated. The blend nanoparticles were prepared by nanoprecipitation method for controlled release of a poorly water-soluble model drug, indomethacin. The drug-loaded nanoparticles were nearly spherical in shape. The particle size and drug loading efficiency slightly decreased with increasing MPEG- b-PCL blend weight ratio. Two distinct thermal decomposition steps from thermogravimetric analysis suggested different blend weight ratios. Thermal transition changes from differential scanning calorimetry revealed miscible blending between MPEG- b-PDLL and MPEG- b-PCL in an amorphous phase. An in vitro drug release study demonstrated that the drug release behaviors depended upon the PDLL block length and the blend weight ratios but not on PCL block length.     

Chlorinating cleavage of silicon–naphthyl bonds of polycarbosilane,and introduction of poly(ethylene glycol) graft copolymer micelles

A new series of polycarbosilanes [(PhCH₂)SiCH₃Cl, Poly B] was designed by chlorinating cleavage reaction of silicon–naphthyl in polycarbosilane. The ¹H spectra of poly B revealed that the SiCH₂ and the SiCH₃ protons peak were up-field shifted compared with the type [(PhCH₂)SiCH₃Np, Poly A] polycarbosilane. Grafted polycarbosilane was synthesized with poly ethylene glycol (PEG) by nucleophilic substitution of the chloride substituents on the polycarbosilane. The aggregation behaviors of graft copolymers were investigated by dynamic light scattering and fluorescence at 25 °C in aqueous solutions of different polyethylene glycol (PEG) substituent.     

Synthesis of α-hydroxy-ω-amino poly(ethylene oxide) and its use in reaction injection moulding (RIM)

Summary Computer simulations show that oligomers with two different terminal groups with dissimilar reactivities for isocyanates give a delayed viscosity rise in polyurethanes. This is a desired behaviour for RIM processes. Therefore, an -hydroxy--amino poly(ethylene oxide) (HAPEO) has been prepared. The synthesis was carried out by the ethoxylation of 2-hydroxyethyl phthalimide as a blocked amine. Hydrazinolysis appears to be the best way to obtain the deblocked oligomer. The product properties were compared with an oligomeric diamine ether (Jeffamine D2000). The gel time of HAPEO (M_n=500) and JAD2000 (M_n=2000) was the same (2 sec.). The product with HAPEO had a higher modulus, a comparable impact and tensile strength and a lower elongation at break.     

Effects of liquid–liquid phase separation on crystallization of poly(ethylene glycol) in blends with isotactic poly(methyl methacrylate)

To analyze the interplay between crystallization and liquid–liquid phase separation (LLPS), isothermal crystallization behavior of poly(ethylene glycol) (PEG) in blends with isotactic poly(methyl methacrylate) (i-PMMA) was investigated by differential scanning calorimetry (DSC). The blend system had an upper critical solution temperature (UCST) type phase diagram. When the crystallization occurred simultaneously with LLPS, the overall crystallization rate was enhanced at high crystallization temperatures T_c, relatively compared with that of neat PEG. This behavior was interpreted by the combination of the effects of spinodal quench depth ?T_s and usual supercooling degree ?T_c, according to the theory of Mitra and Muthukumar, namely, the crystallization rate is enhanced by the concentration fluctuation-assisted nucleation at high T_c. In the crystallization after LLPS proceeded, on the other hand, the overall crystallization rate was slow and less dependent on the blend composition. In addition, it was revealed by small-angle X-ray scattering measurements that amorphous i-PMMA was excluded from the interlamellar region of PEG crystals in SQ as well as WQ.     

Synthesis of amphiphilic macrocyclic graft copolymer consisting of a poly(ethylene oxide) ring and multi-poly(?-caprolactone) lateral chains

A series of amphiphilic macrocyclic graft copolymers composed of a hydrophilic poly(ethylene oxide) as ring and hydrophobic poly(?-caprolactone) as lateral chains with different grafting lengths and densities of side chains were prepared by a combination of anionic ring-opening polymerization and coordination-insertion ring-opening polymerization. The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethyl potassium (DPMK) as co-initiators, and a linear α,ω-dihydroxyl poly(ethylene oxide) with pendant protected hydroxymethyls (l-poly(EO-co-EEGE)) was obtained. The monomer reactivity ratios of these compounds are r_1(EO) = 1.20 ± 0.01 and r_2(EEGE) = 0.76 ± 0.02, respectively. Then the ring closure of l-poly(EO-co-EEGE) was achieved via an ether linkage by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the linear chain-extended polymer was hydrolyzed in acidic conditions first and then purified by treating with α-CD. The pure cyclic copolymer of EO and glycidol (Gly) with multipendant hydroxymethyls [c-poly(EO-co-Gly)] as the macroinitiator was used further to initiate the ring-opening polymerization of ?-caprolactone (CL), and a series of amphiphilic macrocyclic graft copolymers c-PEO-g-PCL were obtained. The final products and intermediates were characterized by GPC, NMR and MALDI-TOF in detail.     

High-efficiency synthesis of dendrimer-like poly(ethylene oxide) via “arm-first” approach

In this study, a dendrimer-like polymer based on poly(ethylene oxide) (PEO) was synthesized through a combination of anionic ring-opening polymerization (AROP) and click reaction via arm-first method. Firstly, the polymeric arm, a linear PEO with one alkynyl group and two bromo groups, was synthesized by AROP of ethylene oxide followed by functionalization with propargyl bromide and esterified with 2-bromopropionic bromide. Second, a star PEO carrying three azide groups was synthesized though AROP of ethylene oxide used 1,1,1-tris(hydrosymethyl) ethane as initiator followed esterificated with 2-bromopropionic acid and azidation. By azide–alkyne click reactions between the azide-terminated PEO star polymer and linear PEO with functionalization alkynyl group, a three generation dendrimer-like PEO, G3-PEO-24Br, was successfully synthesized. The resulting polymers were observed to have precisely controlled molecular weights and compositions with narrow molecular weight distributions.     

Preparation and characterization of poly (ethylene glycol) grafted Ca-alginate fibers by γ-irradiation for biomedical applications

Radiation processing, being a physical process, is an environmentally friendly alternative to chemical modifications. It is economically viable, safe, and possesses several advantages over other conventional methods employed for modification and grafting. To improve the physico-mechanical properties of Ca-alginate fiber (CaAF), poly (ethylene glycol) (PEG) was grafted by applying γ-radiation of different intensities. The effect of γ-irradiation on the physico-mechanical, thermal, morphological, thermal and water aging, water, and simulated body fluid (SBF) uptake were evaluated. FT-IR results confirmed that PEG was successfully grafted onto Ca-alginate fibers by γ-irradiation. From the detailed experimental results, irradiation doses and PEG concentration were optimized for grafting processes. The results showed that 50% PEG and 2.5?kGy irradiation dose yielded the highest tensile strength. Differential scanning calorimetric (DSC) analysis showed that with increasing γ-intensity a decrease of dehydration temperature of the fibers had occurred. On the other hand, the glass transition temperature (T _g) increased with increasing irradiation dose. The tensile cracked surfaces of the grafted alginate fibers were analyzed by scanning electron microscope (SEM) in order to monitor their surface morphologies. The SEM images of the cracked surfaces demonstrated that spherical shape rods were present for irradiated fiber sample while no such rods were observed for non-irradiated fibers. The characteristic data obtained from SBF and water uptake, and water and thermal aging experiments indicated that CaAF grafted with 50% PEG by applying 2.5?kGy γ-irradiation can be potentially employed for biomedical purposes, such as surgical suture.     

Double stimuli responsive mixed aggregates from poly(acrylic acid)-block-poly(ε-caprolactone)-block-poly(acrylic acid) and poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock copolymers

Well defined ABA triblock copolymer comprising a biodegradable poly(ε-caprolactone) (PCL) middle block and two pH responsive poly(acrylic acid) (PAA) outer blocks was synthesized by atom transfer radical polymerization of tert-butyl acrylate, initiated by PCL-based macroinitiator, followed by selective hydrolysis of the poly(tert-butyl acrylate) blocks. The cooperative self-assembly of the synthesized poly(acrylic acid)-block-poly(ε-caprolactone)-block-poly(acrylic acid) (PAA₂₂PCL₂₆PAA₂₂) copolymer with a temperature-responsive poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO₂₆PPO₄₀PEO₂₆, Pluronic P85) triblock copolymer at different compositions in aqueous media was investigated. Based on experimental data, copolymer properties and composition, formation of nano-sized aggregates comprising a mixed PCL/PPO core and a mixed PEO/PAA corona is suggested. The binary mixture of PAA₂₂PCL₂₆PAA₂₂:PEO₂₆PPO₄₀PEO₂₆ copolymers at molar ratio 3:1 favors the formation of mixed aggregates only, while at higher PEO₂₆PPO₄₀PEO₂₆ content the aggregates coexist with pure PEO₂₆PPO₄₀PEO₂₆ micelles.     

Synthesis of biocompatible tadpole-shaped copolymer with one poly(ethylene oxide) (PEO) ring and two poly(ɛ-caprolactone) (PCL) tails by combination of glaser coupling with ring-opening polymerization

The biocompatible tadpole-shaped copolymers [cyclic-poly(ethylene oxide) (PEO)]-b-[linear poly(?-caprolactone) (PCL)]₂ [(c-PEO)-b-PCL₂] with one PEO ring and two PCL tails were synthesized by combination of glaser coupling with ring-opening polymerization (ROP). First, a linear PEO precursor with two alkyne groups at the chain terminal and two hydroxyl groups at the chain middle was prepared by ROP of EO monomer and the following transformation of functional groups. Then, cyclic PEO with two hydroxyl groups at the same site was obtained by the “Glaser” cyclization. Finally, the hydroxyl groups on cyclic PEO directly initiated the ROP of ?-CL monomer to produce the target copolymers (c-PEO)-b-PCL₂. The target copolymers and intermediates were all well characterized by GPC, MALDI-TOF MS, ¹H NMR and FT-IR.     

Degradable poly(ester-ether urethane)s derived of AB2 miktoarm star copolymer poly(ethylene glycol-(ε-caprolactone)2) diol: Synthesis,characterization and degradation

Four different miktoarm star copolymers poly(ethylene glycol-(ε-caprolactone)₂) diol [PEG-PCL₂] were obtained using α-diol-ω-methoxy poly(ethylene glycol) [MPEG-(OH)₂] as macroinitiator/chain transfer agent in the ring opening polymerization (ROP) of ε-caprolactone (CL) catalyzed by tin(II) 2-ethylhexanoate [Sn(Oct)₂]. PEG-PCL₂ and 1,6-hexamethylene diisocyanate (HDI) were used as precursors of a new family of poly(ester-ether urethane)s PEUs. PEUs films were characterized by FT-IR, DSC, mechanical properties, water absorption, hydrolytic degradation and SEM.     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.