Comonomer Content Research Articles

Influence of Molecular Structure on Crystallization Kinetics and Performance of Polyethylene of Raised Temperature Resistance

Two copolymer polyethylenes of raised temperature resistance (PE-RT) were used to analyze their basic properties and molecular structure, including their basic physical properties, molecular weight and distribution, molecular chain structure, and aggregation structure of the product; the crystallization kinetics and other properties differences are also discussed. The results showed that the basic physical properties of the two resins were similar, but there were still some differences in molecular structure. The molecular weight of PE-RT-1 was slightly lower in the range of 500,000–1,000,000 molecular weight, and slightly higher in the range of <500,000 molecular weight than PE-RT-2. The crystallization capacity of the crystallizable part of PE-RT-2 was slightly better than that of PE-RT-1. The comonomer (1-butene) content and polymer branching degree of PE-RT-2 were higher than those of PE-RT-1. The crystallinity of PE-RT-1 products was higher than that of PE-RT-2, and the lattice structure of PE-RT-1 was more complete and had good heat resistance. In addition, the butene content of PE-RT-2 with high molecular weight was higher than those of PE-RT-1, which was more conducive to the generation of tie molecules.

Enhancement the dosimetric properties of N-(3-methoxypropyl) acrylamide polymer gel dosimeter for cancer treatment

Recent studies related to the polymer gel dosimetry technique for radiation therapy have shown the importance of using additive of different concentrations to the polymer gel to improve the dose sensitivity. This work provides a significant improvement on the developed N-(3-methoxypropyl) acrylamide polymer gel dosimeter by incorporated with an inorganic salt of calcium chloride (CaCl2). Nuclear Magnetic Resonance relaxometry read out technique was used to examine dose-response after irradiation by measuring the change in the relaxation rate of R2. A medical linear accelerator with 6 MV photon beams and a 200 cGy/min dose rate was used to irradiate the developed gel with different absorbed doses. It was evidently clear from the findings that the R2 dose sensitivity of the developed polymer gel increased significantly by adding different concentrations of CaCl2 reaching 3.5 times higher than that without salt. The dose-response of the improved gel at various concentrations of co-monomer. Also, the dependency on the radiation dose rate, photon energy and irradiation temperature was investigated. Additionally, the stability of unirradiated as well as irradiated gel for 7-days post-irradiation was reported.

Quasi-alternating copolymerization of oxiranes driven by a benign acetate-based catalyst

Alternating copolymers are distinctly unique in comparison with other copolymers. Herein, an in-depth investigation of the oxyanionic ring-opening copolymerization of propylene oxide (PO) and allyl glycidyl ether (AGE) from benzyl alcohol (BnOH) activated with potassium acetate (KOAc) complexed by 18-crown-6 ether (18C6) is described. We demonstrate that the 18C6/KOAc complex is an efficient and benign catalytic system to promote copolymerization of both oxirane monomers, leading to well-defined polyethers with varied comonomer content and low dispersity values (ƉM < 1.20). Kinetic analysis confirmed the controlled nature of the (co)polymerization process, and the determination of reactivity ratios revealed a quasi-alternating copolymerization profile, according to the Fineman-Ross method. The comparison between the quasi-alternating-type PO/AGE copolymerization and block or gradient copolymerization revealed significant differences, to confirm the different sequence incorporation in the different topological copolymers. These results highlight the great potential of 18C6/KOAc-mediated copolymerization process for the controlled sythesis of a series of copolymer topologies.

Biobased high-performance polyesters: Synthesis and thermal properties of poly(isoidide furanoate) and co-polyesters

A fully biobased high-performance polyester was prepared by the sequential melt polymerization and solid-state post-condensation of the symmetrical 1,4:3,6-dianhydrohexitol isoidide and dimethyl 2,5-furandicarboxylate (FDME). The thermal properties of the resulting poly(isoidide furanoate) were well within the “high-performance” range with a glass transition- and melting temperature of approx. 165 and 280 °C, respectively. Since such a high melting temperature does not allow for conventional melt processing without thermal degradation of the polymer, various C2-C4 diol comonomers were incorporated in an attempt to create semi-crystalline co-polyesters with a high-glass-transition-temperature and sufficiently low melting point. It was found that semi-crystalline co-polyesters could be obtained with either low (3–5 mol%) or high (80–95 mol%) isoidide contents. All semi-crystalline co-polyesters with low diol comonomer contents (≤20 mol%) had still glass transition temperatures ≥ 118 °C despite having low molecular weights. Co-polyesters with a high diol comonomer content had lower melting points than the PiIF homopolymer, as well as a significantly lower glass transition temperature. The molecular weight of the PiIF homopolymer and a semicrystalline poly(ethylene-co-isoidide furanoate) co-polyester could be significantly enhanced by solid-state post-condensation. Thus, poly(isoidide furanoates) are an interesting class of new fully biobased polyesters that has potential in high-performance applications.

Two‐way shape memory properties study of crosslinked cycloolefin/dicyclopentadiene copolymer

AbstractThe two‐way shape memory polymers (2 W‐SMPs) have garnered significant interest from researchers due to their great performance and wide range of applications. In this study, we present the synthesis and assessment of crosslinked copolymers P(CDD‐co‐DCPD) and P(COE‐co‐DCPD) using dicyclopentadiene and different comonomers via ring‐opening metathesis polymerization (ROMP). The two‐way shape memory behavior of these copolymers was altered by not only varying the species and incorporation level of a second comonomer, but also by adjusting the concentration of the second comonomer. The results indicated that the melting and crystalline temperature of the crosslinked copolymer decreased with increasing content of DCPD. Additionally, it was observed that the P(CDD‐co‐DCPD) copolymers exhibited one‐way shape memory function rather than two‐way shape memory performance under constant stress. With the increasing content of DCPD in the copolymers, the shape recovery ratio exhibited an upward trend and reached a maximum of 94.44%. Additionally, the shape fixation ratio of the P(CDD‐co‐DCPD) copolymers also surpassed 95%. In contrast, the P(COE‐co‐DCPD) copolymers demonstrated both one‐way and two‐way shape memory functions, particularly, when the molar content of DCPD was 4 mol%, the shape recovery ratio reached a maximum of 95.03% and the shape fixation ratio exceeded 90%.

Itaconic Acid as a Comonomer in Betulin-Based Thermosets via Sequential and Bulk Preparation.

The inherent chemical functionalities of biobased monomers enable the production of renewably sourced polymers that further advance sustainable manufacturing. Itaconic acid (IA) is a nontoxic, commercially produced biobased monomer that can undergo both UV and thermal curing. Betulin is a biocompatible, structurally complex diol derived from birch tree bark that has been recently studied for materials with diverse applications. Here, betulin, IA, and biobased linear diacids, 1,12-dodecanedioic acid (C12) and 1,18-octadecanedioic acid (C18), were used to prepare thermosets using sequential and bulk curing methods. Thermoplastic polyester precursors were synthesized and formulated into polyester-methacrylate (PM) resins to produce sequential UV-curable thermosets. Bulk-cured polyester thermosets were prepared using a one-pot, solventless melt polycondensation using glycerol as a cross-linker. The structure-property relationships of the thermoplastic polyester precursors, sequentially prepared PM thermosets, and bulk-cured polyester thermosets were evaluated with varying IA content. Both types of thermosets exhibited higher storage moduli, Tgs, and thermal stabilities with greater IA comonomer content. These results demonstrate the viability of using IA as a comonomer to produce betulin-based thermosets each with tunable properties, expanding the scope of their applications and use in polymeric materials.

Large Range Thermochromism in Liquid Crystalline Elastomers Prepared with Intra‐Mesogenic Supramolecular Bonds

AbstractLiquid crystalline elastomers (LCEs) that retain the cholesteric phase (CLCEs) are soft, polymeric materials that retain periodic structure and exhibit a selective reflection. While prior studies have examined thermochromism in CLCEs, the association of temperature change and reflection wavelength shift has been limited to 1.4 nm °C−1. Here, CLCEs with intra‐mesogenic supramolecular bonds are prepared to enhance tunability as well triple the rate (e.g., 4.8 nm °C−1). Specifically, these materials incorporate liquid crystalline monomers based on dimerized oxy‐benzoic acid (OBA) derivatives. Increasing the concentration of the OBA comonomers increases the magnitude of red‐shifting thermochromism of the selective reflection. At and above a threshold concentration, the selective reflection in the CLCEs can disappear upon heating, analogous to on‐off “switching.” Further, the introduction of the supramolecular bonds within the CLCE enable mechanical programming and enhanced one‐time tunable thermochromism via a one‐way shape memory process. Accordingly, this research could enable functional use in low temperature sensitive optical elements, fail‐safe thermal indicators for food packaging, and smart window coatings.

The effect of different prepared TiCl4-MgCl2 catalysts on the behavior of gas-phase ethylene/1-hexene copolymerization

The effect of different prepared magnesium sources including MgCl2 (ZN-THF), metallic magnesium powder (ZN-O), and MGE (ZN-MGE) as the support of titanium-based Ziegler-Natta catalysts on behaviors of gas-phase ethylene/1-hexene copolymerization was investigated. These catalysts reacted with TEA presented higher catalytic activity than using TnOA. This is due to TEA had higher reducing power. Moreover, it revealed that ZN-MGE exhibited the highest activity among other catalysts because ZN-MGE had the highest distribution of titanium contents measured by EDX, and then generated more active sites. The average particle sizes of these catalysts were around 35 µm, which was suitable for commercial application. Considering copolymer size, the size of EH-ZN-O-TEA and EH-ZN-MGE-TnOA (ca. 420 µm) displayed the largest particle size. The large size of EH-ZN-MGE-TnOA was expected due to the agglomeration and steric hindrance of the catalyst reacted with TnOA. For the particle size distribution, only EH-ZN-O-TEA showed the bimodal distribution meaning that both fragmentation and no fragmentation occurred. Other copolymers showed positive-skewed distribution. Typically, the morphologies of copolymer were spheroidal lump without fine particles. The roles of comonomer content on thermal behaviors were presented by melting temperature, C7-soluble content, and crystallinity. It was found that although all catalysts with TEA exhibited higher activity than TnOA, the use of TnOA perhaps tended to facilitate the comonomer insertion. It revealed that steric hindrance of TnOA cocatalyst may retard the copolymer chain attachment. As the result, the comonomer insertion of EH-ZN-MGE was the highest among other catalysts.

How 4-(7-Octen-1-yl)-N,N-diphenylaniline co-units induce strong melt memory effects in isotactic polypropylene random copolymers

The random incorporation of comonomer units in isotactic polypropylene usually disrupts the chemical regularity of the macromolecular chain, thereby remarkably affecting the crystallization and melting processes. We study the influence of a novel comonomer 4-(7-Octen-1-yl)-N,N-diphenylaniline (ODPA), in the concentration range of 1.1–6.8 mol%, on the crystallization and self-nucleation behavior of isotactic polypropylene copolymers. Non-isothermal and isothermal differential scanning calorimetry experiments demonstrated that crystallization kinetics are significantly retarded upon comonomer incorporation as the ODPA co-units are excluded to the amorphous regions. Furthermore, ODPA comonomer incorporation leads to a sharp increase in nucleation density; thus, spherulitic superstructures become significantly smaller. Remarkably, the ODPA co-units induce a strong melt memory effect that can persist even above the equilibrium melting temperature for copolymers with 4.4–6.8 mol% ODPA. The width of Domain IIa (exclusive melt-memory domain), an indicator of the self-nucleation strength, starts to increase sharply once the content of ODPA exceeds 1.8 mol%. In contrast, the width of Domain IIb (self-seeding domain) remains constant. We attribute the self-nucleation effect in these ODPA copolymers to the aggregation of co-units in the interlamellar amorphous regions that hinder, upon melting, the motion of the chain sequences that were initially packed within the crystal lattice. In this way, to reach the isotropic melt state, the sample must be heated to much higher temperatures than its apparent or even equilibrium melting point, depending on the comonomer content. Consequently, nucleation upon cooling from the self-nucleated melt becomes easier and faster.

Comonomer Inclusion in Single Crystals of Isodimorphic Random Copolymers of Butylene Succinate and ε-Caprolactone

Random copolymers exhibit diverse crystallization behavior depending on whether comonomers are excluded or included in the crystalline phase. To understand the crystallization behavior of crystallizable isodimorphic random copolymer, in this work, we selected poly[(butylene succinate)-ran-(ε-caprolactone)], BSxCLy, copolyesters and studied their single crystal structure and morphology. The single crystals of PBS homopolymer and BS-rich copolymers were prepared by the self-seeding method in o-dichlorobenzene. The prepared single crystals were characterized by atomic force microscopy (AFM) and transmission electron microscopy. The suitable seeding temperature and the dissolution temperature of the copolymers decreased with the comonomer content. The morphological features, including size, shape, layer number, and thickness, of the single crystals depend on the seeding temperature, crystallization temperature, and, most interestingly, the composition. The size of the single crystals increased with the seeding temperature, while the aspect ratio increased with the crystallization temperature. Higher CL content in the copolymers contributed to multilayered crystals and curved edges. These characteristics were explained by the difference in growth rate and the number of dislocations, both of which are expected to be influenced by the comonomers. As revealed by AFM, the thickness of the single crystals increased with CL contents, which is the opposite of what has been reported for copolymers with high degree of comonomer exclusion. Electron diffraction of the single crystals showed smaller lattice expansion as compared to melt crystallized samples, indicating a lower degree of comonomer inclusion of CL units.

Detailed microstructure analysis through monomeric insertion modes of poly(propylene-co-norbornene) copolymers and poly(propylene-co-ethylene-co-norbornene) terpolymers with low norbornene contents

Polypropylene-based thermoplastic elastomers continue to be materials of enormous industrial interest because of their high mechanical performance and durability. These materials are especially important, for instance, in the automotive industry, where these polyolefins accounts for up to 32% of the total plastic used in a car. In the search for new grades, poly(propylene-co-ethylene-co-norbornene) terpolymers might be of interest for the production of a new class of thermoplastic elastomers, whose properties could be tailored by controlling the composition, as well as its distribution. Unfortunately, thorough characterization of these materials has not been possible so far, because of the complexity of their 13CNMR spectra. In this work, two series of poly(propylene-co-norbornene) copolymers and poly(propylene-co-ethylene-co-norbornene) terpolymers, containing low molar fractions of norbornene and ethylene-norbornene, respectively, have been synthesized and characterized in detail by NMR analysis. The comparison of 13CNMR spectra in both series and their respective changes with norbornene ratio in the feed enables a complete assignment of signals, which reveals that the terpolymers are featured by a well-defined microstructure, consisting of propylene sequences bound by both PEP triads and well-defined norbornene-ethylene sequences. Such a particular distribution results from an associated insertion of the ethylene and the norbornene that, in addition, accounts for the higher contents of both comonomers, when compared with their respective copolymers, obtained under the same reaction conditions.

Investigate the effect of short chain branching and lamellar thickness on mechanical and optical properties of linear low-density polyethylene by successive self-nucleation/annealing (SSA) technique

In this article, various polyethylenes based on Ziegler-Natta and metallocene catalysts with different comonomer contents were investigated by successive self-nucleation and annealing (SSA) technique. Lamellar thickness, short chain branches content (SCBC) and methyl sequence lengths (MSL) were calculated by the modified Thomson-Gibbs equation and suitable calibration curves available in the literature. Moreover, linear low-density polyethylene (LLDPE) samples with different physical, mechanical and optical properties were investigated according to heat of fusion, the lamellar thickness, SCBC and methyl sequence length (MSL) of the multiple peaks. The results showed that the mechanical and optical properties such as dart drop impact strength, Elmendorf tear resistance, softening point and haze are associated with the lamellar thickness and SCBC of the resins.

Vanadium (III) catalysts with bulky Bis-NHCs ligands for ethylene-norbornene (co)polymerization

A series of vanadium catalysts with bulky bis(N-heterocyclic carbenes) (bis-NHCs) ligands were synthesized by in-situ reaction. With diethylaluminum chloride (AlEt2Cl) as cocatalyst and ethyl trichloroacetate (ETA) as activator, these catalysts exhibit good activity when used to catalyze ethylene (co)polymerization. The structure of the catalyst, especially the bridging carbons number of the bis-NHCs ligands, is related to the performance of the (co)polymer. When the bis-NHCs ligand with tBu substituted, increased the bridging carbons number of the bis-NHCs ligand is easier to obtain higher molecular weight polymers. But when the bis-NHCs ligand with 2,6-diisopropyl phenyl substituted, the increase of the bridging carbons number is not conducive to obtaining higher molecular weight polymers. Under the same concentration of comonomer, the increase of the bis-NHCs ligand bridged carbon number of the V-complexes is more beneficial to obtain the copolymer with high norbornene (NB) content.

Effect of Chemical Composition on Molecular Mobility and Phase Coupling in Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with Different Comonomer Contents

Two series of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with different amounts of hydroxyvalerate (HV) and hydroxyhexanoate (HHx) units are compared. The influence of chemical composition on the molecular mobility in quenched samples is discussed, as well as the consequences on the aptitude to crystallize and the microstructures developed during cold-crystallization. In both quenched PHBHV and PHBHHx, $$T_g$$ decreases as the content of comonomer unit increases. The HHx units (propyl side-groups) are better molecular spacers and produce a stronger $$T_g$$ shift as compared to the HV units (ethyl side-groups). Copolymerization has no striking effect on the width of the glass transition and the cooperativity length in quenched samples, but in cold-crystallized samples the glass transition is dramatically broadened. When the fully amorphous copolymers are heated from the glassy state to room temperature, crystallization occurs but is largely disrupted, suggesting that the molecular environment in the amorphous phase is significantly changed. The HHx units, which are excluded from the host crystals, delay and slow down the crystallization kinetics in a stronger way as compared to the HV units, which can partially co-crystallize. The obtained crystalline phases are prone to reorganization and the residual amorphous phases appear to have strong differences in composition and large density fluctuations. A practical consequence is that microstructures with different coupling between phases, and thus different properties and stability over time, can be obtained by controlling the nature and content of the comonomer units.

Effect of Ethylene Comonomer Content on the Foam Processing Window of Long-Chain Branched Polypropylene

The non-optimized foam processing window (FPW) can create processing challenges and limit the possible materials with which a polymer of interest can be processed in emerging foaming technologies. To address this drawback, we aim to investigate the effect of ethylene comonomer content on the foaming behavior of polypropylene (PP), particularly the FPW. Two PP resins containing 0.75 and 1.5 wt % of ethylene comonomers were studied, while using a PP homopolymer as a control. High-pressure differential scanning calorimetry confirmed the decrease in the onset crystallization (Tc-onset) and end melting (Tm-end) temperatures with increasing ethylene comonomer content as a result of the defects the ethylene units induce in the crystalline structure of PP. Rheological measurements suggest that the addition of ethylene comonomer content resulted in negligible changes in the extensional and shear rheological responses of the PP-based resins. In addition, the foam expansion results and the observed morphologies reveal no significant change in the resins’ foamability, characterized by the shape of their expansion profiles with respect to the foaming temperature. Interestingly, the FPW was found to be the sole affected parameter, as 1.5 wt % of ethylene comonomers resulted in a 10 °C shift in the FPW toward lower temperatures, compared to the PP homopolymer. The resins with 0 and 1.5 wt % of ethylene comonomer content showed similar mechanical responses under compression tests for their optimally expanded samples. These findings reveal a potentially effective approach for tuning the FPW of processed PP resins without compromising their foaming and mechanical performances. Consequently, foam processing techniques are further enhanced, resulting in a wider span of potential applications.

Frontal Polymerization and Three-Dimensional Printing of Thermoset Polymers with Tunable Thermomechanical Properties

On-demand curing of thermoset polymers with tunable mechanical properties is of great interest for a variety of applications. In this work, we demonstrate rapid, solvent-free synthesis of a cross-linked copolymer using thermal frontal polymerization of dicyclopentadiene (DCPD) and linseed oil at ambient temperature. A series of thermoset copolymers with various concentrations of comonomers are readily prepared to produce polymers with a wide range of ultimate elongation (11–360%), elastic modulus (1.1 GPa to 5.6 MPa), and glass transition temperature (120–31 °C). The addition of linseed oil comonomers to DCPD resin to increase the molecular weight between crosslinks reduces the available energy density for frontal polymerization and improves the elastomeric properties of the produced polymers. Increasing the concentration of linseed oil comonomers results in highly stretchable and flexible elastomers with self-recovery capability after large mechanical deformations. The DCPD resin and the resin containing 50 wt % of linseed oil comonomers are used to demonstrate three-dimensional (3D) printing of stiff and flexible cellular structures, respectively. This study is the first demonstration of low-cost, facile, and energy-efficient 3D printing of stretchable elastomers via frontal polymerization.

Critical insights into ethylene‐1‐alkene copolymers and long‐chain branched polyethylene microstructure on thermo‐rheological and sealing behavior of multicomponent systems

AbstractThe microstructure‐property relationships in multicomponent ethylene‐1‐alkene copolymers with different branching in the microstructures are demonstrated. The metallocene catalyzed linear low density polyethylene (mLLDPE), was miscible with both autoclave grade low density polyethylene (LDPE‐A) and/or tubular grade low density polyethylene (LDPE‐T). For these multicomponent systems, the rheological response was distinctly differentiating and sensitive to the microstructure of LDPE, at higher shear regimes. The thicker lamellae of LDPE‐T and/or LDPE‐A might co‐crystallize if there is a high density polyethylene‐like fraction present in the mLLDPE. Even though the macro parameters like density and melt index (MI) of the investigated multicomponent systems are comparable, the subtle differences in the microstructure manifested by type and distribution of comonomer and/or branching affected the sealing performance. Both high comonomer content and comonomer distribution in the mLLDPE matrix affording a higher fraction of material melting below 120°C were found to be critical for the heat sealing. The fraction of material melting at lower temperatures, attributed to the tertiary branches present in the hyper‐branched microstructure of LDPE‐A, participate in the sealing process, and lower the sealing temperature. It was evident that mLLDPE with asymmetric distribution of lamellae is more sensitive to the microstructure of the LDPE used.

New Liquid Crystalline Elastomeric Films Containing a Smectic Crosslinker: Chemical and Physical Properties

Side-chain liquid crystal elastomers (SC-LCEs) have been designed by using a new smectic crosslinker. Two types of monodomain films were prepared based on polysiloxane chains, with a different relative concentration of both crosslinker and mesogenic comonomers. The mesomorphic behavior of the two SC-LCE systems was investigated by differential scanning calorimetry and polarized optical microscopy showing a different mesomorphic behavior: in one case, we obtained a nematic SC-LCE film, in the other case, a Smectic A SC-LCE film. In both systems, the mesophases were stable in a wide temperature range. Moreover, the SC-LCE films possess a relatively high orientation at room temperature. The physical-chemical properties, such as the local orientational ordering, structural organization, and dynamics of SC-LCEs’ constituents were studied by means of static and dynamic 2H NMR experiments, small-angle X-ray, and wide-angle X-ray diffractions. The relevant physical properties, such as the thermo-elastic and thermo-mechanic behaviors, are reported and discussed in view of the practical applications.

Propylene/Cyclic Olefin Copolymers with Cyclopentene, Cyclohexene, Cyclooctene, Tricyclo[6.2.1.0(2,7)]undeca-4-ene, and Tetracyclododecene: The Synthesis and Effect of Cyclic Structure on Thermal Properties

Propylene (P) copolymers with a series of cyclic olefins [cyclopentene (CPE), cyclohexene (CHE), cis-cyclooctene (COE), tricyclo[6.2.1.0(2,7)]undeca-4-ene (TCUE), and tetracyclododecene (TCD)] have been prepared in toluene in the presence of phenoxide-modified half-titanocene catalysts, especially Cp’TiCl2(O-2,6-iPr2C6H3) (Cp’ = 1,2,4-Me3C5H2, tBuC5H4), and methylaluminoxane (MAO) cocatalyst. The resultant copolymers are amorphous materials, and their compositions were uniform as confirmed by DSC thermograms [sole glass transition temperatures (Tg)]. The cyclic olefins were incorporated in a 1,2-insertion manner, and the incorporation was affected by the kind of cyclic olefin as well as the nature of catalysts employed. The CHE contents in the copolymers were up to 6.3 mol % (incorporated in an isolated manner), whereas the CPE, COE, TCUE, and TCD contents in the copolymers increased up to ca. 40 mol % (with a mixture of isolated and alternating incorporations) with an increase in the comonomer concentration charged. Linear correlations between Tg values and cyclic olefin contents were demonstrated in all copolymers. The cyclic structure affects the Tg values in the propylene copolymers, except that plots of Tg values vs cyclic olefin contents were close in the P/CPE and P/COE copolymers. In the low cyclic olefin content region (up to 25 mol %), the Tg values in the propylene copolymers were higher than those in the ethylene copolymers.

Elastomeric copolyesters of ω-pentadecalactone and cyclohexylenedimethylene succinate obtained by enzymatic polymerization

The use of renewable monomers and green polymerization processes for preparing new synthetic polymers is a hot topic today. In this work we have obtained high molecular weight copolyesters derived from ω-pentadecalactone (PDL), dimethyl succinate (DMS) and 1,4-cyclohexanedimethanol (1,4-CHDM) by a combination of ring opening polymerization (ROP) and two step melt polycondensation processes. The reaction has been carried in bulk under mild conditions (80–120 °C) and catalyzed by immobilized Candida artarctica lipase B (N435 biocatalyst). These reactions were followed by 1H NMR and it was observed that although PDL reacted faster, at the end copolyesters displayed a random microstructure due to transesterification reactions taking place during polymerization. These copolyesters were thermally stable up to around 350 °C and semicrystalline for all compositions with melting temperatures decreasing with the increased content of the counterpart comonomer up to a pseudo-eutectic point located at 40 mol-% of PDL composition. The crystalline structure and transitions taken place by heating have been studied by WAXS and SAXS synchrotron X-ray diffraction. Copolyesters with elastomeric properties could be obtained at intermediate compositions.