Types Of Copolymers Research Articles

Influence of Compounding Parameters on Color Space and Properties of Thermoplastics with Ultramarine Blue Pigment.

The incorporation of thermoplastics with pigments imparts diverse aesthetic qualities and properties to colored thermoplastic products. The selection of pigment type and content, along with specific processing conditions, plays a pivotal role in influencing color properties and overall product performance. This study focuses on optimizing these parameters to ensure the desired color quality and product functionality. Two types of polypropylene copolymer (PPCP) with different melt flow rates (MFRs) and acrylonitrile butadiene styrene (ABS) were compounded with ultramarine blue pigment masterbatch (MB) in concentrations ranging from 1 to 5 wt.% using a twin-screw extruder. The compounding process was conducted at a constant screw speed of 200 rpm and a die temperature of 210 °C. The effects of screw speed and die temperature were investigated at a constant MB of 3 wt.%. Colored samples were fabricated by injection molding. Microscopic analysis revealed a well-dispersed pigment within the PPCP matrix when using the MB. Rheological properties, assessed through the power law index, confirmed effective pigment dispersion, facilitated by shear thinning behavior and controlled shear rate via the manipulation of screw speed and die temperature. The effects of masterbatch contents and processing conditions on color spaces were evaluated using CIELAB and CIELCH, with one-way ANOVA employed to identify statistical significance. Higher opacity in high-MFR PPCP and ABS resulted in increased lightness and color strength, surpassing low-MFR PPCP by 15-40% at equivalent MB contents. Masterbatch content emerged as a significant factor influencing the color spaces of all colored thermoplastics. Further analysis, including Fisher pairwise comparisons of one-way ANOVA, revealed that screw speed influenced the redness and hue of low-MFR PPCP, whereas die temperature affected the lightness and hue of high-MFR PPCP and ABS. Interestingly, the blueness and chroma of colored thermoplastics were minimally affected by both screw speed and die temperature. Notably, regardless of processing conditions, the flexural properties of colored thermoplastics remained comparable to the neat polymer when incorporated with ultramarine blue pigment masterbatch.

Polyolefin Blends with Selectively Crosslinked Disperse Phase Based on Silane-Modified Polyethylene.

Polypropylene-based multiphase compositions with a disperse elastomer phase provide superior impact strength. Making this property indifferent to processing steps requires stabilization of the morphology of these materials. Various approaches have been tested over time, each of which shows limitations in terms of performance or applicability. Using polyethylene (PE) homo- and copolymers capable of silane-based crosslinking as modifiers was explored in the present study, which allows decoupling of the mixing and crosslinking processes. Commercial silane-copolymerized low-density PE (LD-PEX) from a high-pressure process and silane-grafted high-density PE (HD-PEX) were studied as impact modifiers for different types of PP copolymers, including non-modified reference PE grades, LDPE and HDPE. Blends based on ethylene-propylene random copolymers (PPR) and based on impact- (PPI) and random-impact (PPRI) copolymers show improvements of the stiffness-impact balance; however, to different degrees. While the absolute softest and most ductile compositions are achieved with the already soft PPRI copolymer base, the strongest relative effects are found for the PPR based blends. Modifiers with lower density are clearly superior in the toughening effect, with the LD-PEX including acrylate as second comonomer sticking out due to its glass transition around -40 °C. The impact strength improvement found in most compositions (except at very high content) results, however, not from the expected phase stabilization. For comparable systems, particle sizes are normally higher with crosslinking, probably because the process already starts during mixing. Thermoplastic processability could be retained in all cases, but the drop in melt flow rate limits the practical applicability of such systems.

One-pot, surfactant-free synthesis of poly(styrene-N,N′-methylenebis(2-propenamide)-acrylic acid) and poly(styrene-N,N′-methylenebis(2-propenamide)-methacrylic acid) microspheres for adsorptive removal of heavy metal ions

Two copolymer microspheres, poly(styrene-N,N′-methylenebis(2-propenamide)-acrylic acid) (PS-MBA-AA) and poly(styrene-N,N′-methylenebis(2-propenamide)-methacrylic acid) (PS-MBA-MAA), were synthesized through a surfactant-free one-pot copolymerization method, rendering them easily prepared. Through the utilization of scanning electron microscopy (SEM), laser particle size analysis, Fourier transform infrared spectroscopy (FTIR), BET adsorption-desorption isotherms, and energy dispersive spectrometry (EDS), the structures of PS-MBA-AA and PS-MBA-MAA were meticulously examined. These analyses provided substantial evidence that the copolymer microspheres possess a relatively uniformity in terms of both particle size and composition. The copolymer microspheres, PS-MBA-AA and PS-MBA-MAA, demonstrate remarkable efficiency in the rapid adsorption of Cu2+, Pb2+, and Cd2+. Notably, they possess the ability to achieve over 80% of their equilibrium adsorption capacity within a mere 10 min. It is worth noting that both types of copolymers exhibit superior adsorption efficacy and anti-coexisting ion interference, particularly in relation to Pb2+ among the three of heavy metal ions.

The Halophilic Bacterium Paracoccus haeundaensis for the Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) from Single Carbon Sources.

The study objective was to evaluate the potential production of polyhydroxyalkanoates (PHAs), a biodegradable plastic material, by Paracoccus haeundaensis for which PHA production has never been reported. To identify the most effective nitrogen-limited culture conditions for PHAs production from this bacterium, batch fermentation using glucose concentrations ranging from 4 g l-1 to 20 g l-1 with a fixed ammonium concentration of 0.5 g l-1 was carried out at 30°C and pH 8.0. A glucose supplement of 12 g l-1 produced the highest PHA concentration (1.6 g l-1) and PHA content (0.63 g g-1) thereby identifying the optimal condition for PHA production from this bacterium. Gas chromatography-mass spectrometry analysis suggests that P. haeundaensis mostly produced copolymer types of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] from glucose concentrations at 12 g l-1 or higher under the nitrogen-limited conditions. When several other single carbon sources were evaluated for the most efficient PHA production, fructose provided the highest biomass (2.8 g l-1), and PHAs (1.29 g l-1) concentrations. Results indicated that this bacterium mostly produced the copolymers P(3HB-co-3HV) from single carbon sources composing a range of 93-98% of 3-hydroxybutyrate and 2-7% of 3-hydroxyvalerate, whereas mannose-supplemented conditions produced the only homopolymer type of P(3HB). However, when propionic acid as a secondary carbon source were supplemented into the media, P. haeundaensis produced the copolymer P(3HB-co-3HV), composed of a 50% maximum monomeric unit of 3-hydroxyvaleric acid (3HV). However, as the concentration of propionic acid increased, cell biomass and PHAs concentrations substantially decreased due to cell toxicity.

Electrochemical Properties and Structure of Membranes from Perfluorinated Copolymers Modified with Nanodiamonds.

In this study, we aimed to design and research proton-conducting membranes based on Aquivion®-type material that had been modified with detonation nanodiamonds (particle size 4-5 nm, 0.25-5.0 wt. %). These nanodiamonds carried different functional groups (H, OH, COOH, F) that provided the hydrophilicity of the diamond surface with positive or negative potential, or that strengthened the hydrophobicity of the diamonds. These variations in diamond properties allowed us to find ways to improve the composite structure so as to achieve better ion conductivity. For this purpose, we prepared three series of membrane films by first casting solutions of perfluorinated Aquivion®-type copolymers with short side chains mixed with diamonds dispersed on solid substrates. Then, we removed the solvent and the membranes were structurally stabilized during thermal treatment and transformed into their final form with -SO3H ionic groups. We found that the diamonds with a hydrogen-saturated surface, with a positive charge in aqueous media, contributed to the increase in proton conductivity of membranes to a greater rate. Meanwhile, a more developed conducting diamond-copolymer interface was formed due to electrostatic attraction to the sulfonic acid groups of the copolymer than in the case of diamonds grafted with negatively charged carboxyls, similar to sulfonic groups of the copolymer. The modification of membranes with fluorinated diamonds led to a 5-fold decrease in the conductivity of the composite, even when only a fraction of diamonds of 1 wt. % were used, which was explained by the disruption in the connectivity of ion channels during the interaction of such diamonds mainly with fluorocarbon chains of the copolymer. We discussed the specifics of the mechanism of conductivity in composites with various diamonds in connection with structural data obtained in neutron scattering experiments on dry membranes, as well as ideas about the formation of cylindrical micelles with central ion channels and shells composed of hydrophobic copolymer chains. Finally, the characteristics of the network of ion channels in the composites were found depending on the type and amount of introduced diamonds, and correlations between the structure and conductivity of the membranes were established.

Development of ionic polymer metal composite actuator by EB graft-polymerization

Ionic polymer-metal composites (IPMC) actuators were fabricated by applying ionic exchange groups such as sulfonic acids and carboxylic acids using EB graft-polymerization to two types of fluorine-based copolymers (Poly (tetrafluoroethylene-co-hexafluoropropylene): FEP and Poly (ethylene-co-tetrafluoroethylene): ETFE) as base materials, and then forming electrodes with Pt-Pd by sputtering. The physical properties of the obtained graft membrane and the evaluation as an actuator were performed. It was suggested that the acrylic acid graft membrane is preferable for PEM as components of IPMC actuator, because the ion conduction mechanism is a vehicle mechanism in which oxonium ions pass through formed hydrated clusters in PEM. In the case of operation at 10 V, IPMC actuator based on the acrylic acid-grafted FEP and ETFE showed similar or larger displacement than that based on conventional membrane. The grafted ETFE, which has high mechanical properties, is superior to the grafted FEP used in the actuators. Therefore, it was found that the ETFE grafted with acrylic acid is preferable for the IPMC actuator.

Production of Graft Copolymers of Cod Collagen with Butyl Acrylate and Vinyl Butyl Ether in the Presence of Triethylborane-Prospects for Use in Regenerative Medicine.

Collagen is a suitable material for regenerative medicine because it is characterized by its good biocompatibility. However, due to its fibrillar structure, it cannot organize itself into three-dimensional porous structures without additional modification. The introduction of synthetic monomer elements into the collagen macromolecules is a technique used to form three-dimensional, collagen-based, branched, and crosslinked structures. New types of graft copolymers made from cod collagen with a butyl acrylate and vinyl butyl ether copolymer in aqueous dispersion were obtained in the presence of triethylborane by a radical mechanism. The process of graft copolymer formation proceeded as usual by radical initiation, through radicals formed during triethylborane oxidation by oxygen residues, collagen borination, and reversible inhibition with the participation of a boroxyl radical. The characteristics of the graft copolymers were determined using methods of physical and chemical analysis (GPC, SEM, IR spectroscopy, etc.), while the cytotoxicity was assessed using the MTT assay method. It is shown that the grafting of alternating blocks of butyl acrylate and vinyl butyl ether to the protein macromolecules results in changes in the morphological pattern of the graft co-polymer in comparison with native collagen. This is manifested in the development of consolidations around the collagen fibers of the structural matrices, with the co-polymer cellular structure consisting of interpenetrating pores of unequal size. Additionally, it is important that the graft co-polymer solutions are not toxic at a certain concentration. The above properties confirm the promising nature of the technique's application as the basis for producing new materials for regenerative medicine.

Biodegradable block copolymer as compatibilizer and blend component of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-based polyester blends

Atactic poly(3-hydroxybutyrate) (PHB)-b-poly(ε-caprolactone) (PCL) diblock copolymer, a type of biodegradable block copolymer (BCP) was selected as compatibilizer for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)/PCL immiscible blends. The additive effect of BCP on the morphologies and mechanical properties was dependent on the blend composition of PHBH/PCL. For 80/20 (w/w) PHBH/PCL blends, the incorporation of BCP did alter their mechanical properties by the increase in elongation at break with increasing BCP amount. However, the addition of BCP for 60/40 (w/w) PHBH/PCL blends were not greatly affected on their morphologies and mechanical properties. When BCP was used as one of binary blend components, the mechanical properties were significantly changed depending on the blend composition. PHBH/BCP blends also showed promising improvement in terms of mechanical performance. Presence of BCP in the ternary and binary blend systems decreased the enzymatic degradation rate by PHB depolymerase.

Pyrolysis GC-MS Characterization of Plastic Debris from the Northern Gulf of Alaska Shorelines

Plastics and their breakdown components are accumulating at alarming rates in global ecosystems, including the Gulf of Alaska. Obtaining knowledge of the chemical composition of plastics is important because different types of plastics are manufactured using different types of polymers and copolymers for specialized applications. We employed pyrolysis GC-MS for the chemical characterization of 115 plastic debris samples of different physical and optical properties nonrandomly collected from shorelines in the northern Gulf of Alaska. A two-tier approach of peak fingerprinting and mass spectral data of marker peaks provided higher confidence in the data. The analyses did not appear to be compromised by the physical properties, optical properties, or weathering conditions of the debris. Polyethylene and polypropylene, the low-density floating plastics possibly of oceanic origins, were some of the most frequently detected polymers in the Katmai National Park and Preserve and Kenai Fjords National Park. Interestingly, a more diverse composition of polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate), and poly(vinyl chloride) was detected in Western Prince William Sound shorelines, possibly of oceanic as well as terrestrial origins. Additional benefits of the pyrolysis GC-MS method included the detection of copolymers and plastic additives in the same analytical runs.

Crystal Structure Analysis of Different Flame Retardant Copolymers

In this paper, through the DSC rising and cooling scanning and non-isothermal crystallization tests of different flame retardant copolymers, the crystallization process of four types of copolymers formed by adding different flame retardants such as CEPPA, DDP, Carbon-dots (gCDs), and MOF materials was studied. Also, the crystallization kinetics and crystal structure were explored. The results showed that the flame retardant effect of the flame retardant copolymer was improved after adding gCDs. The subcooling temperature (ΔTmc) values of MOF material and CEPPA were both higher than those of the DDP flame retardant copolymer after the addition of carbon dots, indicating that the introduction of the carbon-dots material made crystallisation easier. With the increase of carbon dot content, the value first increases and then decreases, indicating that the crystallization is the easiest when the content is 1%, and 1% gCDs+8% DDP has a higher crystallization ability. Pure DDP has the highest mc values, which also shows good spinnability. Also, the cooling rate strongly influences the crystallisation process, with crystallisation being more rapid when the crystallisation rate is higher. Also, the cooling rate strongly influence the crystallisation process, with crystallisation being more rapid when the crystallisation rate is higher.

Polyacrylamide-Based Block Copolymer Bearing Pyridine Groups Shows Unexpected Salt-Induced LCST Behavior

Thermal-responsive block copolymers are a special type of macromolecule that exhibit a wide range of applications in various fields. In this contribution, we report a new type of polyacrylamide-based block copolymer bearing pyridine groups of polyethylene glycol-block-poly(N-(2-methylpyridine)-acrylamide; Px) that display distinct salt-induced lower critical solution temperature (LCST) behavior. Unexpectedly, the phase-transition mechanism of the salt-induced LCST behavior of Px block copolymers is different from that of the reported LCST-featured analogues. Moreover, their thermo-responsive behavior can be significantly regulated by several parameters such as salt species and concentration, urea, polymerization degree, polymer concentration and pH values. This unique thermal behavior of pyridine-containing block copolymers provides a new avenue for the fabrication of smart polymer materials with potential applications in biomedicine.

Water-soluble PEG segmented mannose-based macromolecules: Synthesis, characterization and their biocompatibility

The macromolecular architectures, namely mannose-based methacrylate acetyl-mannopyranoside and PEG block copolymers [AB type copolymer [PEG-b-PMAM], poly(ethyleneglycol)-b-poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside) and ABA type copolymer [PMAM-b-PEG-b-PMAM], poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside)-b-poly(ethyleneglycol)-b-poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside)] were synthesized by atom transfer radical polymerization (ATRP) method that were deacetylated to generate the corresponding water-soluble and biocompatible glycopolymer macromolecules. The molecular weight of acetyl and deacetylate macromolecules was in the range of 7083–9499 and 4659–6026, as determined by GPC and proton NMR spectra. The 5 % decomposition temperatures for acetylated methacrylate macromolecules (218–299 °C) were higher than the corresponding water-soluble macromolecules (204–248 °C). The conjugation of poly(methacryl-2,3,4,6-tetra-O-acetyl-D-mannopyranoside) (PMAM) segment with the PEG block decreased the glass transition (Tg) value, and the water-soluble macromolecules displayed Tg in the range of 92–95 °C. The biocompatibility of the synthesized water-soluble mannose-based macromolecules was determined using Human Bone Derived Cells (HBDC) culture with the TCP (Tissue culture plastic) template as control. Using three different concentrations of the synthesized glycopolymers, HBDC's were cultured for 1, 3, and 7 days. The effect of mannomethacrylate macromolecules on mitochondrial activity of HBDC's was estimated using colorimetry that showed the conversion of MTS [3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium-bromide] to formazan (MTS assay). ABA type diblock copolymer architecture exhibited increased absorbance values of 3 and 7 day cultures at 1–100 M concentrations, with the highest values observed at a concentration of 1 M for day 3 cultures. The design of these novel mannose-based macromolecules is important for improving cell proliferation, cell adhesion, and osteointegration efficiency.

Self-assembly of block copolymers on surfaces exposed to space-confined solvent vapor annealing

We apply here an optimized polymer processing approach, based on solvent vapor annealing in a space-confined environment, to generate previously unrevealed self-assembled microstructures comprised of periodic lamellar or hexagonal nanostructures of molecular dimensions, depending on the type of block copolymer that is used.

Recent Advances on PEO-PCL Block and Graft Copolymers as Nanocarriers for Drug Delivery Applications.

Poly(ethylene oxide)-poly(ε-caprolactone) (PEO-PCL) is a family of block (or graft) copolymers with several biomedical applications. These types of copolymers are well-known for their good biocompatibility and biodegradability properties, being ideal for biomedical applications and for the formation of a variety of nanosystems intended for controlled drug release. The aim of this review is to present the applications and the properties of different nanocarriers derived from PEO-PCL block and graft copolymers. Micelles, polymeric nanoparticles, drug conjugates, nanocapsules, and hybrid polymer-lipid nanoparticles, such as hybrid liposomes, are the main categories of PEO-PCL based nanocarriers loaded with different active ingredients. The advantages and the limitations in preclinical studies are also discussed in depth. PEO-PCL based nanocarriers could be the next generation of delivery systems with fast clinical translation. Finally, current challenges and future perspectives of the PEO-PCL based nanocarriers are highlighted.

Characterization of Cyclic Olefin Copolymers for Insulin Reservoir in an Artificial Pancreas

Type-1 diabetes is one of the most prevalent metabolic disorders worldwide. It results in a significant lack of insulin production by the pancreas and the ensuing hyperglycemia, which needs to be regulated through a tailored administration of insulin throughout the day. Recent studies have shown great advancements in developing an implantable artificial pancreas. However, some improvements are still required, including the optimal biomaterials and technologies to produce the implantable insulin reservoir. Here, we discuss the employment of two types of cyclic olefin copolymers (Topas 5013L-10 and Topas 8007S-04) for an insulin reservoir fabrication. After a preliminary thermomechanical analysis, Topas 8007S-04 was selected as the best material to fabricate a 3D-printed insulin reservoir due to its higher strength and lower glass transition temperature (Tg). Fiber deposition modeling was used to manufacture a reservoir-like structure, which was employed to assess the ability of the material to prevent insulin aggregation. Although the surface texture presents a localized roughness, the ultraviolet analysis did not detect any significant insulin aggregation over a timeframe of 14 days. These interesting results make Topas 8007S-04 cyclic olefin copolymer a potential candidate biomaterial for fabricating structural components in an implantable artificial pancreas.

Fabrication of Ordered Porous Polyimide Films Templated by (AB)m Type of Diblock Copolymer.

Ordered porous polyimide films were fabricated from (AB)m type of diblock copolymer polyimide-b-polystyrene (PI-b-PS). An increase in PS volume fraction (f VPS) is beneficial to decrease the relative dielectric constants and water contact angles of the obtained porous PI films: the relative dielectric constant decreases to 1.89 and water contact angle decreases to 43° when f VPS is 0.36, indicating porous PI films can be used as low-κ material and have good wettability. The solvent uptake of the porous PI films increases with increasing f VPS. A net-like morphology appears when f VPS reaches 0.36. The net-like porous PI film reaches equilibrium uptake of water within approximately 2.5 h, with a final equilibrium uptake ratio of 17.5%, and reaches equilibrium uptake of toluene within approximately 8 h, with a final equilibrium uptake ratio of 15.4%, displaying the highest and fastest solvent uptake compared with other microstructured porous PI films, which is ascribed to the specific characteristic of the interconnecting porous channels derived from the self-assembly of PI-b-PS with f VPS 0.36. Introducing thermally degradable segments to PI-based block copolymer is an effective method to prepare porous PI films and can enhance some of their properties.

An equation driven quality classification of (a)symmetric gradient, gradient-block, block-gradient-block and block copolymers

The control of the A/B comonomer distribution over individual chains targeting block and/or gradient monomer distributions is essential to control the macroscopic properties of the resulting copolymers. Matrix-based kinetic Monte Carlo simulations allow to compare each chain of a representative copolymer sample with the desired (mathematical) composition, as defined by monomer inclusion probabilities (PA/B) taking the B-functionalization degree (B-Func) as maximally 50%. A so-called average deviation (SD∗ value) results per chain, with a close to 0 average (normalized) structural deviation 〈SD〉 corresponding to an almost perfect structure and a 〈SD〉 close to 1 representing the worst case scenario of a B-homopolymer. The previously assigned 〈SD〉 transitions from excellent to good and from good to poor are, however, somewhat arbitrary, e.g. for both symmetric gradient and block copolymers a threshold 〈SDGood/Poor〉 of 0.3 is currently utilized and only for specific asymmetric cases (30% B-Func block, block-gradient, and gradient) 〈SDExc/Good〉 and 〈SDGood/Poor〉 values have been reported. The present work puts forward an equation driven method to obtain 〈SD〉 threshold values, minimizing the arbitrary nature of the quality classification for a given copolymer type and more importantly aligning the quality assessment for any copolymer type containing block and/or gradient elements. Emphasis is on the complete SD distribution (instead of only its average) for (a)symmetric AB gradient, block A-gradient AB, block A-gradient AB-block B, and AB block copolymers by introducing the overall gradient and block fractions (fGr/Bl) as a novel parameter alongside the targeted degree of polymerization (target DP) and B-Func. Ideal theoretical structures with equal chain length and a perfect implementation of the desired PA/B profiles are dealt with, as they represent the best case an actual synthesis recipe could deliver in the limit. It is shown that the log-normal distribution can be reliably used to approximate the SD distribution, as coefficients of determination (R2) very close to one follow for (a)symmetric copolymers . It is further showcased that threshold values for gradient dominant structures must be higher than those for block-like structures and that well-defined symmetric structures are more difficult to achieve than asymmetric ones. It is also recommended to report 〈SD〉 together with its standard deviation σSD.

Multiresponsive Dielectric Metasurfaces Based on Dual Light‐ and Temperature‐Responsive Copolymers

AbstractTunability is essential for unlocking a range of practical applications of high‐efficiency metasurface‐based nanophotonic devices and systems. Increased research efforts in this area during recent years led to significant progress regarding tuning mechanisms, speed, and diverse active functionalities. However, so far almost all the demonstrated works are based on a single type of physical stimulus, thereby excluding important opportunities to enhance the modulation range of the metadevices, the available design options, as well as interaction channels between the metadevices and their environment. In this article, it is experimentally demonstrated that multi‐responsive metasurfaces can be realized by combining asymmetric, highly resonant metasurfaces with multi‐responsive polymeric materials. The respective copolymers combine light‐ and temperature‐responsive comonomers in an optimized ratio. This work demonstrates clearly reversible light‐responsive, temperature‐responsive, and co‐responsive tuning of the metasurface optical resonance positions at near‐infrared wavelengths, featuring maximum spectral resonance shifts of nearly twice the full‐width‐at‐half‐maximum and accompanied by more than 60% absolute modulation in transmittance. This work provides new design freedom for multifunctional metadevices and can potentially be expanded to other types of copolymers as well. Furthermore, the studied hybrid multiresponsive systems are promising candidates for multi‐dimensional sensing applications.

Modulating chemical composition of the D-π-D-A-D type copolymers to obtain soluble Neutral-state green or dark Yellowish-black films with Multi-color electrochromism

Novel high-performance D-π-D-A-D type polymeric electrochromic materials consisting of phenylene π-bridged core alternated with the donor cyclopentadithiophene derivatives and the D-A-D moiety thiophene-diketopyrrolo[3,4-c]pyrrole-thiophene (TDPPT), differing by the ratio of donor to acceptor units incorporated, were achieved by Suzuki cross-coupling reaction. The polymer films displayed intense dual visible absorptions in their neutral states, which were modulated both in the positions and relative intensities by regulating the chemical composition as well as the donor-to-acceptor ratio in the polymer backbone, allowing the facile manipulation of the neutral-state colors. The polymer PBDC-1 exhibited a deep green neutral-state color. PBDC-2 and PBDC-3 also demonstrated two strong and broad absorptions, but a relative small gap of transmission in the orange-yellow region, giving the films dark yellowish-black color. In situ optical monitoring revealed that all the polymers underwent surprising multi-color variations upon the redox cycling, simultaneous with fast switching speeds, high coloration efficiencies, and large optical contrasts.

Memory of crystallization in the melt of commercial linear low density polyethylenes processed in an open twin-screw extruder

Compared with a constant recrystallization rate of commercial linear low density polyethylenes (LLDPE) as a function of melt temperature, copolymers reprocessed in an open twin-screw extruder, display the expected strong melt-memory features upon melting followed by recrystallization. Precipitation from dilute solution had the same effect on melting-recrystallization of commercial copolymers. In the twin-screw melt re-processing, a small content of long-chain branches and crosslinks are incorporated to the copolymer's structure, but especially a further consumption of additives uncovers self-nucleation features that speed up recrystallization and are related to the major copolymer microstructure. The observed difference in re-crystallization behavior between metallocene type and Ziegler-Natta (ZN) type copolymers, both with equivalent average comonomer content and molecular mass, is due to the inter-chain comonomer distribution. While for metallocene-made and low density polyethylenes, below a critical melt temperature the recrystallization rate increases continuously with decreasing melt temperature, in broadly distributed ZN copolymers there is an inversion of the temperature gradient of the rate at the onset of liquid-liquid phase separation (LLPS). The mass fraction of highly branched molecules required to observe the onset of LLPS via melting followed by recrystallization was evaluated from the TREF profiles, and the effect of self-nucleated melts at different levels on the overall spherulitic morphology was observed via polarized optical microscopy.