Random Copolymers Research Articles

Visible light-driven organocatalyzed radical ring-opening polymerization of Bicyclo[1.1.0]butanes

Radical ring-opening polymerization (rROP) offers an essentially practical strategy to introduce a broad scope of functional groups in the polymer backbone. While suitable cyclic monomers mostly possess a vinyl group to facilitate the radical addition step, we herein present an efficient rROP of highly strained bicyclo[1.1.0]butane (BCB)-derived monomers through radical addition to bridge σ-carbon–carbon bond by photoinduced electron/energy transfer reversible addition−fragmentation chain transfer (PET-RAFT) polymerization technique, producing poly(BCBs) with relatively predictable molecular wight and low to moderate dispersity. Spatiotemporal control over the polymer chain-growth was achieved and high chain-end fidelity was imparted to access intriguing random and block copolymers with complex structures.

Synthesis of mannose conjugated biodegradable polyester-based nanocarriers and their binding study with Concanavalin A

In this paper, we aim to create fully biodegradable glyconanoparticles formed via self-assembly of glycopolymers, comprising of biodegradable aliphatic polyester conjugated with mannose moiety. To accomplish the goal, a series of random copolymers comprised of poly(propargyl glycolide-co-lactide) were synthesized. Alkyne moiety of the poly (propargyl glycolide) component was then clicked with mannose ethyl azide to produce amphiphilic glycopolymers in good yield (60–75 %). The glycopolymers were then self-assembled to form glyconanoparticles of 15–23 nm size in dry state and 78–88 nm size in hydrated state (hydrodynamic diameter). The copolymers were characterized by NMR and FTIR, whereas the nanoparticles were thoroughly characterized by DLS, FESEM, and HR-TEM and explored for their lectin binding efficiency. Isothermal calorimetry (ITC) experiments suggest a stronger binding efficiency of glyconanoparticles towards mannose-specific lectin such as Concanavalin A, as compared to its corresponding glycopolymers (∼2 fold) and monomeric mannose unit (∼7-fold) as well. Moreover, curcumin was selected as the model drug to be encapsulated (∼76 % encapsulation efficiency) and released (74 % in 24 h) from the glyconanoparticles. Apart from these, excellent haemocompatibility, cell viability, and cellular uptake of the nanoparticles (more than 80 % cells showed uptake of the nanoparticles), further supported their potential as drug carriers having sugar as a targeting moiety.

Effect of polycarbonate (PC) content on the mechanical properties, morphology and transesterification mechanism of PBT/PC immiscible blends

AbstractThis study focuses on the experimental investigation of the mechanical properties of PBT/PC blends with varying compositions. The studied mechanical properties include tensile strength, elongation, tensile modulus, impact strength, and Shore hardness of PBT/PC blends with different PC contents. PBT, characterized by its semi‐crystalline and tough nature, contrasts with PC, known for its impact resistance and hardness. Achieving an optimal blend composition proves to be crucial for attaining the best combination of these properties. The tensile strength of the PBT/PC 30/70 blend increased by approximately 24%, with Shore hardness also experienced a 12% enhancement compared to pure PBT. This improvement is attributed to the presence of PC segments in the blend structure. Conversely, an increase in PC content led to the elongation and impact strength of the blends peaking in the PBT/PC 70/30 blend. Notably, the impact strength of the PBT/PC blend with 30% PC increased by about three times compared to PBT and 18% more than pure PC. Scanning Electron Microscopy (SEM) analysis revealed that PBT and PC segments disperse at lower PC content, while at higher content, phase separation becomes prominent. Fourier Transform Infrared Spectroscopy (FTIR) analysis indicates direct transesterification between PBT and PC, resulting in the formation of a long‐chain blend structure with random copolymer blocks. The transesterification mechanism is also supported by Differential Scanning Calorimetry (DSC) results, wherein a reduction in the crystallization temperature (Tc) and an increase in the glass transition temperature (Tg) is observed. The study concludes that the volume of these segments and their bonding play a decisive role in determining the mechanical properties. The bonding mechanism elucidated through FTIR and SEM provides valuable insights into the fabrication and property engineering of PBT/PC blends.

Substrate Neutrality for Obtaining Block Copolymer Vertical Orientation.

Nanopatterning methods utilizing block copolymer (BCP) self-assembly are attractive for semiconductor fabrication due to their molecular precision and high resolution. Grafted polymer brushes play a crucial role in providing a neutral surface conducive for the orientational control of BCPs. These brushes create a non-preferential substrate, allowing wetting of the distinct chemistries from each block of the BCP. This vertically aligns the BCP self-assembled lattice to create patterns that are useful for semiconductor nanofabrication. In this review, we aim to explore various methods used to tune the substrate and BCP interface toward a neutral template. This review takes a historical perspective on the polymer brush methods developed to achieve substrate neutrality. We divide the approaches into copolymer and blended homopolymer methods. Early attempts to obtain neutral substrates utilized end-grafted random copolymers that consisted of monomers from each block. This evolved into side-group-grafted chains, cross-linked mats, and block cooligomer brushes. Amidst the augmentation of the chain architecture, homopolymer blends were developed as a facile method where polymer chains with each chemistry were mixed and grafted onto the substrate. This was largely believed to be challenging due to the macrophase separation of the chemically incompatible chains. However, innovative methods such as sequential grafting and BCP compatibilizers were utilized to circumvent this problem. The advantages and challenges of each method are discussed in the context of neutrality and feasibility.

Flash precipitation of random copolymers in a micro-mixer for controlling the size and surface charge of nanoparticles.

Precisely controlling the size and surface chemistry of polymeric nanoparticles (P-NPs) is critical for their versatile engineering and biomedical applications. In this work, various NPs of amphipathic random copolymers were comparatively produced by the flash nanoprecipitation (FNP) method using a tube-in-tube type of micro-mixer up to 330 mg min-1 in production scale in a kinetically controlled manner. The NPs obtained from poly(styrene-co-maleic acid), poly(styrene-co-allyl alcohol), and poly(methyl methacrylate-co-methacrylic acid) were concurrently controlled in the range 51-819 nm in size with narrow polydispersity index (<0.1) and -44 to -16 mV in zeta potential, by depending not only on the polymeric chemistry and the concentration but also the mixing behavior of good solvents (THF, alcohols) and anti-solvent (water) under three flow regimes (laminar, vortex and turbulence, turbulent jet). Moreover, the P(St-MA) derived NPs under turbulent jet flow conditions were post-treated in the initial solution mixture for up to 16 h, resulting in lowering of the zeta potential to -52 mV from the initial -27 mV and decreasing size to 46 nm from 50 nm by further migration of hydrophilic segments with -COOH groups on the outer surface, and the removal of THF trapped in the hydrophobic core.

Microscopic Interaction of Oleated Cellulose and Silica in Dual-Filled Elastomers

The quantification of interactions between fillers and filler with elastomers in nanocomposites relies on the combination of different microscopy techniques. Small Angle X-ray scattering is a key method for the identification of the filler network morphology at the nanoscale. Hybrid nanocomposites containing fillers with diverse morphology and reinforcing ability represent considerable complexity thereby justifying ongoing research in this area, as a consequence of the multiple interactions between fillers and also the filler with the elastomer. Therefore, a microscopic structural investigation of a dual-filled elastomer for tire applications is presented. Chemically modified micro-fibrillated cellulose in combination with traditional silica filler dispersed by melt processing in a styrene-butadiene (SBR) random copolymer were investigated. Small-Angle-X-ray Scattering and Scanning-transmission-electron-microscopy (STEM) revealed non-mixing of the two fillers on the silica scale and the predominant formation of individual filler clusters. Through a novel data deconvolution procedure, partial structure functions corresponding to the contribution of each filler to the scattering function were extracted. This approach offers a suitable methodology to identify the compatibility between morphologically different fillers and their mutual effect on the dispersion.

Study of the Thermal Phase Transition of Poly(N,N-diethylacrylamide-co-N-ethylacrylamide) Random Copolymers in Aqueous Solution.

N-alkyl-substituted polyacrylamides exhibit a thermal coil-to-globule transition in aqueous solution driven by an increase in hydrophobic interactions with rising temperature. With the aim of understanding the role of N-alkyl substituents in the thermal transition, this study focuses on the molecular interactions underlying the phase transition of poly(N,N-diethylacrylamide-co-N-ethylacrylamide) random copolymers. Poly(N,N-diethylacrylamide) (PDEAm), poly(N-ethylacrylamide) (PNEAm), and their random copolymers were synthesized by free radical polymerization and their chemical structure characterized spectroscopically. It was found that the values of the cloud-point temperature increased with PNEAm content, and particle aggregation processes took place, increasing the negative charge density on their surface. The cloud-point temperature of each copolymer decreased with respect to the theoretical values calculated assuming an absence of interactions. It is attributed to the formation of intra- and interchain hydrogen bonding in aqueous solutions. These interactions favor the formation of more hydrophobic macromolecular segments, thereby promoting the cooperative nature of the transition. These results definitively reveal the dominant mechanism occurring during the phase transition in the aqueous solutions of these copolymers.

P‐187: Pretilt angle of liquid crystal molecules induced by photo‐aligned films of Polymerized 2‐(methacrylic acid) ethyl 3,5‐diaminobenzoic acid reaction monomer polyimide for PSVA technology

Orientation film is a key material in liquid crystal displays, and the technology of inducing liquid crystal molecular orientation through polyimide photoorientation film is widely studied. In this work, polyimide is a random copolymer synthesized from a mixture of cyclobutanetetracarboxylic dianhydride and pyromellitic dianhydride, 4,4' ‐ diaminodiphenylmethane, 3,3', 5,5'‐ tetramethylbenzidine, and Methanone, bis (4‐aminophenyl) ‐, homopolymer. In this study, we investigated the pre‐inclination of a series of photo‐crosslinked diamine structures for the polymerization of RM monomers by PSVA (Polymer Stabilized Vertical Alignment) technology, and mainly investigated the pre‐inclination of a series of light‐oriented films with different molar fraction reaction monomers polymerized on the backbone. The results show that the polymerization of 2‐(methacrylate)ethyl ester 3,5‐diaminobenzoic acid reaction monomer with 6.3% molar fraction of polyimide photooriented film achieves high pre‐tilt adjustment under low light accumulation conditions, and successfully achieves excellent optical &amp; reliability performance.

Effect of tetrahydrofuran on the anionic copolymerization of 4‐trimethylsilylstyrene with isoprene

AbstractThe statistical anionic copolymerization of 4‐trimethylsilylstyrene (TMSS) with isoprene (I) in cyclohexane was investigated using in situ near‐infrared (NIR) spectroscopy in the presence of various amounts of the polar modifier tetrahydrofuran (THF). Polymers with narrow molecular weight distribution of 85–138 kg/mol and dispersities of 1.09–1.22 were obtained. By increasing modifier content, the reactivity ratios can be adjusted over a wide range from rTMSS &lt; rI to rTMSS &gt;&gt; rI. Compared to the system styrene/isoprene (S/I) only a minute amount of modifier (0.5 eq THF relative to lithium) is sufficient to alter the reactivity ratios, resulting in an ideally random copolymerization, which validates the higher reactivity of TMSS compared to styrene. Using these reactivity ratios, molar and volume composition gradients were calculated. Additionally, the glass transition temperature and microstructure of the polyisoprene units were investigated via differential scanning calorimetry and proton nuclear magnetic resonance. The results are encouraging for the use of these materials in high‐end applications like membranes.

Synthesis and Kinetic Simulation of Polyampholyte via Free Radical Random Copolymerization

Synthesis and Kinetic Simulation of Polyampholyte via Free Radical Random Copolymerization

Block copolymers as anion exchange membrane in fuel cells

Anion exchange membranes play a crucial part as the primary component of alkaline fuel cells, yet their optimization remains an ongoing endeavor. While research and development efforts have made strides in advancing anion exchange membranes, a pressing need exists to further refine their mechanical properties, ionic conductivity, and chemical stability, especially in comparison to proton exchange membranes. Block copolymers have emerged as promising candidates among the array of materials explored for enhancing anion exchange membranes due to their inherent advantages. These copolymers offer unparalleled flexibility in adjustment and boast superior mechanical properties, making them highly adaptable for modifying anion exchange membranes to meet desired specifications. In order to demonstrate the benefits of block copolymer, this paper primarily summarizes and examines the techniques for varying the material content, investigating composition to identify the block copolymer anion exchanging membrane with exceptional performance characteristics, and contrasting it with the random copolymer, polymer blend, and homopolymer exchange membrane. The results unequivocally demonstrate the efficacy of block copolymers in improving the material structure of exchange membranes by fine-tuning the polymer content. Notably, block copolymers outperform other copolymers in significantly enhancing the performance metrics of anion exchange membranes. In summary, studying block copolymers is a practical way to significantly enhance the performance and functionality of anionic exchange membranes, which will help the alkaline fuel cell industry move toward greater sustainability

Hybrid Nanoparticles from Random Polyelectrolytes and Carbon Dots.

The present study concerns the preparation of hybrid nanostructures composed of carbon dots (CDs) synthesized in our lab and a double-hydrophilic poly(2-dimethylaminoethyl methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate) (P(DMAEMA-co-OEGMA)) random copolymer through electrostatic interactions between the negatively charged CDs and the positively charged DMAEMA segments of the copolymer. The synthesis of P(DMAEMA-co-OEGMA) copolymer was conducted through RAFT polymerization. Furthermore, the copolymer was converted into a strong cationic random polyelectrolyte through quaternization of the amine groups of DMAEMA segments with methyl iodide (CH3I), and it was subsequently utilized for the complexation with the carbon dots. The molecular, physicochemical, and photophysical characterization of the aqueous solution of the copolymers and their hybrid nanoparticles was conducted using dynamic and electrophoretic light scattering (DLS, ELS) and spectroscopic techniques, such as UV-Vis, fluorescence (FS), and FT-IR spectroscopy. In addition, studies of their aqueous solution using DLS and ELS showed their responsiveness to external stimuli (pH, temperature, ionic strength). Finally, the interaction of selected hybrid nanoparticles with iron (III) ions was confirmed through FS spectroscopy, demonstrating their potential application for heavy metal ions sensing.

Target-Oriented Synthesis of Triphenylphosphine Functionalized Carbon Dots with Negative Charge for ROS Scavenging and Mitochondrial Targeting.

Triphenylphosphine functionalized carbon dots (TPP-CDs) showcase robust mitochondria targeting capacity owing to their positive electrical properties. However, TPP-CDs typically involve complicated synthesis steps and time-consuming postmodification procedures. Especially, the one-step target-oriented synthesis of TPP-CDs and the regulation of TPP linkage modes remain challenges. Herein, we propose a free-radical-initiated random copolymerization in combination with hydrothermal carbonation to regulate the TPP backbone linkage for target-oriented synthesis of triphenylphosphine copolymerization carbon dots (TPPcopoly-CDs). The linkage mechanism of random copolymerization reactions is directional, straightforward, and controllable. The TPP content and IC50 of hydroxyl radicals scavenging ability of TPPcopoly-CDs are 53 wt % and 0.52 mg/mL, respectively. TPP serves as a charge control agent to elevate the negatively charged CDs by 20 mV. TPPcopoly-CDs with negative charge can target mitochondria, and in the corresponding mechanism the TPP moiety plays a crucial role in targeting mitochondria. This discovery provides a new perspective on the controlled synthesis, TPP linkage modes, and mitochondrial targeting design of TPP-CDs.

Strategies to Enhance the Electrochromic Properties of Conjugated Polymers Bearing Pyromellitic Diimide Acceptors.

A series of conjugated polymers bearing thiophene-based donors and pyromellitic diimide (PMDI) acceptor were prepared, and their electrochromic (EC) properties were studied via using fabricated thin-film EC devices. It was observed that structurally regular alternating polymers with fewer (1 and 2) thiophene donors do not exhibit any EC properties while increasing the number of donors eventually led to the emergence of orange-red-to-green colour switching. On this basis, two more random co-polymers containing higher donor-to-acceptor ratios were synthesized to further improve EC switching properties. The two polymers, which bear a PMDI-to-thiophene ratio of ca. 1 : 7 and 1 : 8, revealed orange red-to-blue colour switching and generally improved optical contrasts and switching speeds in both the visible and near infra-red (NIR) region. In addition, the subtle modulation of polymer colour and hue via variation of the number of thiophene donors was evident through colorimetric study. This work therefore demonstrates the potential and possibility of using the PMDI acceptor unit to construct EC-active conjugated polymers, and considerations for future tuning of colour and switching performances.

Effect of Block Copolymer Self-Assembly on Phase Separation in Photopolymerizable Epoxy Blends.

Directing self-assembly of photopolymerizable systems is advantageous for controlling polymer nanostructure and material properties, but developing techniques for inducing ordered structure remains challenging. In this work, well-defined diblock or random copolymers were incorporated into cationic photopolymerizable epoxy systems to investigate the impact of copolymer architecture on self-assembly and phase separated nanostructures. Copolymers consisting of poly(hydroxyethyl acrylate)-x-(butyl acrylate) were prepared using photoiniferter polymerization to control functional group placement and molecular weight/polydispersity. Prepolymer configuration and concentration induced distinctly different effects on the resin flow and photopolymerization kinetics. The diblock copolymer self-assembled into nanostructured phases within the resin matrix, whereas the random copolymer formed an isotropic mixture. Rapid photopolymerization and ambient temperature conditions during cure facilitated retention of the self-assembled phases, leading to considerably different composite morphology and thermomechanical behavior. Increased loading of the diblock copolymer induced long-range ordered cocontinuous structures. Even with nearly identical prepolymer composition, controlled nanophase separation resulted in significantly enhanced tensile properties relative to those of the isotropic system. This work demonstrates that controlling phase separation with a block copolymer architecture allows access to nanostructured photopolymers with unique and enhanced properties.

Intrinsically Stretchable Organic Thermoelectric Polymers Enabled by Incorporating Fused-Ring Conjugated Breakers.

While research on organic thermoelectric polymers is making significant progress in recent years, realization of a single polymer material possessing both thermoelectric properties and stretchability for the next generation of self-powered wearable electronics is a challenging task and remains an area yet to be explored. A new molecular engineering concept of "conjugated breaker" is employed to impart stretchability to a highly crystalline diketopyrrolepyrrole (DPP)-based polymer. A hexacyclic diindenothieno[2,3-b]thiophene (DITT) unit, with two 4-octyloxyphenyl groups substituted at the tetrahedral sp3-carbon bridges, is selected to function as the conjugated breaker that can sterically hinder intermolecular packing to reduce polymers' crystallinity. A series of donor-acceptor random copolymers is thus developed via polymerizing the crystalline DPP units with the DITT conjugated breakers. By controlling the monomeric DPP/DITT ratios, DITT30 reaches the optimal balance of crystalline/amorphous regions, exhibiting an exceptional power factor (PF) value up to 12.5 µW m-1 K-2 after FeCl3-doping; while, simultaneously displaying the capability to withstand strains exceeding 100%. More significantly, the doped DITT30 film possesses excellent mechanical endurance, retaining 80% of its initial PF value after 200 cycles of stretching/releasing at a strain of 50%. This research marks a pioneering achievement in creating intrinsically stretchable polymers with exceptional thermoelectric properties.

Correlating Aggregation Ability of Polymer Donors with Film Formation Kinetics for Organic Solar Cells with Improved Efficiency and Processability.

Film formation kinetics significantly impact molecular processability and power conversion efficiency (PCE) of organic solar cells. Here, two ternary random copolymerization polymers are reported, D18─N-p and D18─N-m, to modulate the aggregation ability of D18 by introducing trifluoromethyl-substituted pyridine unit at para- and meta-positions, respectively. The introduction of pyridine unit significantly reduces material aggregation ability and adjusts the interactions with acceptor L8-BO, thereby leading to largely changed film formation kinetics with earlier phase separation and longer film formation times, which enlarge fiber sizes in blend films and improve carrier generation and transport. As a result, D18─N-p with moderate aggregation ability delivers a high PCE of 18.82% with L8-BO, which is further improved to 19.45% via interface engineering. Despite the slightly inferior small area device performances, D18─N-m shows improved solubility, which inspires to adjust the ratio of meta-trifluoromethyl pyridine carefully and obtain a polymer donor D18─N-m-10 with good solubility in nonhalogenated solvent o-xylene. High PCEs of 13.07% and 12.43% in 1 cm2 device and 43 cm2 module fabricated with slot-die coating method are achieved based on D18─N-m-10:L8-BO blends. This work emphasizes film formation kinetics optimization in device fabrication via aggregation ability modulation of polymer donors for efficient devices.

Recyclable elastomers with high mechanical performance and vibration-damping property via triple dynamic bonds

Enhancing the mechanical properties of vibration-damping elastomers with dynamic bonds is crucial for practical applications. Herein, we synthesize recyclable damping elastomers with superior mechanical strength through the incorporation of triple dynamic bonds. Firstly, linear polymers with carboxyl and imidazole groups are fabricated by random copolymerization, which consist of dual dynamic bonds (hydrogen bonds and ionic bonds). Then, 1,4-phenylenediboronic acid is introduced by solution blending and can form boron/nitrogen coordination bonds with imidazole groups, thereby converting dual dynamic bonds into triple dynamic bonds. Therefore, the resulting elastomer exhibits remarkable tensile strength of 16.29 MPa, toughness of 73.53 MJ/m3, and damping properties (maintaining tan δ > 0.3 over a temperature range of 75 °C). Furthermore, owning to the triple dynamic bonds, the elastomer retains exceptional mechanical and vibration-damping properties even after three times of recycling. This work provides a simple strategy to fabricate recyclable elastomers with high mechanical performance and vibration-damping property, which have promising and sustainable potential for practical damping applications.

Polymeric surfactants with high acid values for emulsion type pressure-sensitive adhesives

Low molecular weight polymers with hydrophobic-carboxyl groups have been usually used as anionic surfactants in emulsion polymerization for coatings. However, such polymeric surfactants usually have low acid values below 200, because it is difficult to make high acid-value polymeric surfactants using a normal batch reactor. In this work, we polymerized high acid value polymeric surfactant having high acid values successfully up to 380 using CSTR (continuous stirring tank reactor). The synthesized polymeric surfactant was a random copolymer of P(BA-AA) and we applied them as anionic surfactants in making emulsion-type acrylic PSAs (Pressure-Sensitive Adhesives) to investigate the effects of high acid values on the adhesive properties. This CSTR can effectively control the composition and molecular weight of polymeric surfactants through varying monomer ratios, retention time, and initiator concentrations. The surface tension analysis and emulsion stability test indicated that the synthesized polymeric surfactants exhibited a similar levels of critical micelle concentration (CMC) and emulsion stability with other conventional anionic surfactants. Also, the adhesion property analysis showed that the PSA used high acid value polymeric surfactant resulting in superior adhesive properties and heat resistance than the PSAs used low acid value polymeric surfactant or conventional low molecular weight surfactant. It was very notable that polymeric surfactants having unusually high acid values above 300 because of their high contents of carboxylic acid groups could result in superior adhesive properties and heat resistance.

Facile and rapid synthesis method of dielectric nanocomposite for simultaneous enhancement of electromagnetic wave absorbing/shielding characteristics

The present study involves the fabrication of poly[4-(2-thiophene)aniline] (PTA) nanocomposite for absorption-dependent shielding applications, demonstrating enhanced absorption and small reflection properties. The Microwave absorption characteristics of the fabricated polymer were studied at different loading ratios, resulting in a minimum reflection loss (RLmini) of − 44 dB for the 8 wt % loading ratio. The macromolecular architecture of the PTA material offers higher dielectric loss resulting from higher conduction and interfacial loss. Additionally, the shielding performance is also evaluated, and the sample containing 8 wt % filler demonstrates an impressive − 36.5 dB shielding efficacy. The performance of polymers is significantly impacted by their unit periodic order arrangement. Conducting polymers with linear structure and special π-orbitals angles possess unique characteristics in comparison to their branched and the random copolymer, making them highly sought after as efficient organic conductors, magnetic substances, electrochromic materials, and high dielectric agents. Monomer units contained two periodical cyclic structures and the creation of the inductive effects of heteroatoms elongates the conjugation and reduces the energy bandgap difference between the HOMO and LUMO levels, enabling smoother electron flow and enhancing absorption capacity. The findings indicate that PTA nanocomposite is a promising radar-absorbing coating material due to its superior absorption ability and outstanding shielding performance.