Arrangement Of Polymer Chains Research Articles

Polyaniline/graphitic carbon nitride/reduced graphene oxide ternary nanocomposite film for flexible thermoelectric application

The present study outlines the preparation of a ternary nanocomposite film comprising of polyaniline doped with camphor sulfonic acid (PANI), reduced graphene oxide (rGO), and graphitic carbon nitride (g-C3N4), and delves into its thermoelectric performance. PANI is known to possess high electrical conductivity (σ) and poor thermal conductivity (κ). However, its potential for thermoelectric applications is constrained by the low value of the Seebeck coefficient (S). The incorporation of g-C3N4in PANI has been demonstrated to result in an improvement of the Seebeck coefficient. Furthermore, the addition of rGO to the PANI/g-C3N4sample counteracts the decrease in electrical conductivity. The PANI/g-C3N4/rGO ternary nanocomposite film exhibits an enhanced Seebeck coefficient of ∼2.2 times when compared to the PANI sample. The Seebeck coefficient of the PANI/g-C3N4/rGO nanocomposite is enhanced by the energy filtering effect that occurs at the interfaces between g-C3N4/PANI and PANI/rGO. Theπ-πinteraction between the PANI chains and rGO is responsible for the increased electrical conductivity resulting from the well-ordered polymer chain arrangement on the g-C3N4and rGO surfaces. The ternary nanocomposite sample demonstrated a synergistic improvement in both electrical conductivity and Seebeck coefficient, resulting in a remarkable ∼4.6-fold increment in power factor and an ∼4.3-fold enhancement in the figure of merit (zT), as compared to the pristine PANI film.

Synthesis of long-chain aliphatic poly(β-thioester)s via thiol-Michael polyaddition and their applications in noble metal recovery and information encryption

Long-chain aliphatic polyesters are recognized as the most promising polyethylene mimics in that these materials show comparative physicochemical properties to polyolefins and own the unique merits of degradability and/or recyclability. Nevertheless, the application scenarios of these polymers are rather limited owing to the lack of functional groups. Herein, sulfur atoms are incorporated into the microstructures of long-chain aliphatic polyesters to decipher the variations of physicochemical properties upon replacing specific methylene units by thioether moieties and simultaneously impart polyethylene-like materials with functionalities. First of all, high molecular weight polyesters P1-P4 and poly(β-thioester)s P5-P8 were obtained via condensation polymerization and thiol-Michael polyaddition, respectively. As for phase transition behaviors, poly(β-thioester)s show inferior crystallization/melting temperatures and the corresponding enthalpy changes than their polyester counterparts, and a loosely packed crystalline structure should be responsible for such thermal property degradation. It is reasonable that replacing specific methylene units of long-chain aliphatic polyesters by sulfur atoms, the much bulkier functional entities, will definitely cause great disturbance to the regular arrangement of polymer chains. The rapid hydrolytic degradation of poly(β-thioester)s in acidic and alkaline media can be ascribed to the easy penetration of water molecules into their incompact amorphous/crystalline regions. In the meantime, these poly(β-thioester)s exhibit great prospects in noble metal recovery and information encryption (optical anticounterfeiting). For instance, poly(β-thioester) P5 is an excellent adsorbent to abstract gold ions from water due to its outstanding metal coordination capability. Moreover, poly(β-thioester) P5 emits bright blue photoluminescence in concentrated solution and solid state upon UV irradiation as a result of the clustering-triggered through space electron delocalization and rigidified polymer chain conformation.

Engineering Tough and Elastic Polyvinyl Alcohol‐Based Hydrogel with Antimicrobial Properties

Hydrogels have been extensively used for tissue engineering applications due to their versatility in structure and physical properties, which can mimic native tissues. Although significant progress has been made toward designing hydrogels for soft tissue repair, engineering hydrogels that resemble load‐bearing tissues is still considered a great challenge due to their specific mechanophysical demands. Herein, microporous, tough, yet highly compressible poly(vinyl alcohol) (PVA)‐based hydrogels are reported for potential applications in repairing or replacing different load‐bearing tissues. The synergy of freeze‐thawing and the Hofmeister effect, which controlled the spatial arrangement and aggregation of polymer chains, facilitated the formation of microstructured frameworks with tunable porosity. While the maximum mechanical strength, toughness, and stretchability of the engineered hydrogel were ≈390 kPa, ≈388 kJ m−3, and ≈170%, respectively, Young's modulus based on compression testing wasfound to be in the range of ≈0.02–0.30 MPa, highlighting the all‐in‐one mechanically enriched nature of the hydrogel. Furthermore, the minimal swelling and degradation rate of the engineered hydrogel met the specific requirements for load‐bearing tissues. Finally, excellent antibacterial resistance as well as in vitro biocompatibility of the hydrogel demonstrates its potential for the replacement of load‐bearing tissues.

Oxidation of cellulose fibers using LPMOs with varying allomorphic substrate preferences, oxidative regioselectivities, and domain structures

Lytic polysaccharide monooxygenases (LPMOs) are excellent candidates for enzymatic functionalization of natural polysaccharides, such as cellulose or chitin, and are gaining relevance in the search for renewable biomaterials. Here, we assessed the cellulose fiber modification potential and catalytic performance of eleven cellulose-active fungal AA9-type LPMOs, including C1-, C4-, and C1/C4-oxidizing LPMOs with and without CBM1 carbohydrate-binding modules, on cellulosic substrates with different degrees of crystallinity and polymer chain arrangement, namely, Cellulose I, Cellulose II, and amorphous cellulose. The potential of LPMOs for cellulose fiber modification varied among the LPMOs and depended primarily on operational stability and substrate binding, and, to some extent, also on regioselectivity and domain structure. While all tested LPMOs were active on natural Cellulose I-type fibers, activity on the Cellulose II allomorph was almost exclusively detected for LPMOs containing a CBM1 and LPMOs with activity on soluble hemicelluloses and cello-oligosaccharides, for example NcAA9C from Neurospora crassa. The single-domain variant of NcAA9C oxidized the cellulose fibers to a higher extent than its CBM-containing natural variant and released less soluble products, indicating a more dispersed oxidation pattern without a CBM. Our findings reveal great functional variation among cellulose-active LPMOs, laying the groundwork for further LPMO-based cellulose engineering.

Enhancing gas separation performance of polyimide with Tröger’s bases: Unveiling the impact on polymer and carbon molecular sieve membranes

The potential of carbon molecular sieve membranes (CMSM) for gas separation is widely recognized, and the key precursor for these membranes is polyimide (PI). This study focuses on enhancing the gas separation properties of CMSMs by introducing a unique structural element, Tröger’s bases, into polyimides, resulting in the creation of five distinct polyimides containing Tröger’s bases (PI-TBs). The incorporation of Tröger’s bases has a profound impact on the arrangement of polymer chains within the PIs, leading to a substantial improvement in gas permeability without compromising selectivity. Following carbonization at 600 °C, the resultant CMSMs exhibit significantly enhanced gas permeability while preserving, and in some cases, improving gas selectivity. Among the various types of diamines considered, the 6FDA variant of PI-TB stands out, boasting outstanding gas permeability with a H2 permeability of 4991.0 Barrer and a H2/CH4 selectivity of 30.7; this level of performance surpasses the 2015 Robeson’s upper bound. Furthermore, thermal analysis coupled with mass spectrometry (TG-MS) reveals that the pyrolysis of Tröger’s bases commences prior to that of polyimide. This sequential degradation process facilitates the formation of pyridine N and promotes the π-stacking of PI chains; both of which are instrumental in maintaining excellent gas selectivity. These findings provide valuable insights into the roles of Tröger’s bases in enhancing the gas separation performance of PIs and CMSMs, offering a promising avenue for further advancements.

High Interfacial Shear Strength and High Tensile Strength in Heterocyclic Aramid Fibers with Improved Interchain Interaction

AbstractAs a typical kind of high‐performance fibers, heterocyclic aramid fibers are widely used to reinforce resins to prepare advanced lightweight composites with high mechanical performances. However, their poor interfacial shear strength limits the combination with resins and leads to undesirable interfacial strength of composites. Thus, heterocyclic aramid fibers with high interfacial shear strength and high tensile strength are highly desired. Herein, heterocyclic aramid fibers with a high interfacial shear strength of 40.04 ± 2.41 MPa and a high tensile strength of 5.08 ± 0.24 GPa are reported, in which the nitrile‐modified poly‐(benzimidazole‐terephthalamide) polymer chains are crosslinked by azide‐functionalized graphene oxide nanosheets. The improved interchain interaction can conquer the splitting of nanofibrils and strengthen the skin‐core layer of heterocyclic aramid fibers, while the graphene oxide can induce an ordered arrangement of polymer chains to improve the crystallinity and orientation degree of fibers. These two effects account for the high interfacial shear strength and high tensile strength of heterocyclic aramid fibers. These findings have provided a strategy to efficiently enhance the interfacial shear strength as well as the tensile strength of high‐performance fibers.

Integrated FRET Polymers Spatially Reveal Micro- to Nanostructure and Irregularities in Electrospun Microfibers.

A spatial view of macroscopic polymer material properties, in terms of nanostructure and irregularities, can help to better understand engineering processes such as when materials may fail. However, bridging the gap between the molecular-scale arrangement of polymer chains and the spatially resolved macroscopic properties of a material poses numerous difficulties. Herein, an integrated messenger material that can report on the material micro- to nanostructure and its processes is introduced. It is based on polymer chains labeled with fluorescent dyes that feature Förster resonance energy transfer (FRET) dependent on chain conformation and concentration within a host polymer material. These FRET materials are integrated within electrospun polystyrene microfibers, and the FRET is analyzed by confocal laser scanning microscopy (CLSM). Importantly, the use of CLSM allows a spatial view of material nanostructure and irregularities within the microfibers, where changes in FRET are significant when differences in fiber geometries and regularities exist. Furthermore, changes in FRET observed in damaged regions of the fibers indicate changes in polymer conformation and/or concentration as the material changes during compression. The system promises high utility for applications where nano-to-macro communication is needed for a better understanding of material processes.

Microstructural Model of Indacenodithiophene-co-benzothiadiazole Polymer: π-Crossing Interactions and Their Potential Impact on Charge Transport.

Morphological and electronic properties of indacenodithiophene-co-benzothiadiazole (IDTBT) copolymer with varying molecular weights are calculated through combined molecular dynamics (MD) and quantum chemical (QC) methods. Our study focuses on the polymer chain arrangements, interchain connectivity pathways, and interplay between morphological and electronic structure properties of IDTBT. Our models, which are verified against GIWAXS measurements, show a considerable number of BT-BT π-π interactions with a (preferential) perpendicular local orientation of polymer chains due to the steric hindrance of bulky side chains around IDT. Although our models predict a noncrystalline structure for IDTBT, the BT-BT (interchain) crossing points show a considerable degree of short-range order in spatial arrangement which most likely result in a mesh-like structure for the polymer and provide efficient pathways for interchain charge transport.

Rationally designed fluorinated aromatic polyamide membrane for stable air dehumidification

Membrane based dehumidification technology has attracted wide attention. The anti-hydrolytic property of the membrane holds a significant role in its long-term operation in a wet environment. Herein, a series of fluorinated aromatic polyamides (FPA) are first proposed for stable air-dehumidification. Amide bond offers superior hydrolytic stability over chemical bond in the present dehumidification membrane. The deliberately introduced bulky fluorinated group (-CF3) increases the water permeability and enhances the anti-hydrolytic property of the FPA membranes. The membrane separation performance and membrane stability are further tuned by adjusting the molar ratio of para- and meta-amide groups to optimize the intermolecular forces and polymer chain arrangement, which is verified by the refractive index data and wide-angle X-ray diffraction results. The obtained co-FPA membranes exhibit tunable gas and water vapor permeation properties. With increasing para-amide group content, the gas and water vapor permeability of copolyamides gradually decreases and the selectivity of H2O/N2 increases. Meanwhile, the hydrolytic stability of the co-FPA membranes increases with the increase of TPC content as verified by 1H NMR, GPC, and mechanical property tests. Among these co-FPA membranes, the co-FPA-70 membrane exhibits the most excellent hydrolytic stability. The membrane shows almost no change in 1H NMR spectra and 97% retention of tensile strength after 5000 h of hydrolysis reaction. In the meanwhile, it shows excellent separation stability with a water vapor permeability retention of 74% during long-term hydrolysis aging operation. This study demonstrates the great potential of polyamide for the fabrication of dehumidification membranes with high hydrolysis resistance.

Tuning interchain cavity of fluorinated polyimide by DABA for improved gas separation performance

Fluorinated polyimides with biphenyl structure and –CF3 with rigid chain structure exhibit great potential in membrane-based gas separation. However, the comprehensive separation performance of this type polyimides is not competitive as a gas separation material. Structure regulation is of great significance to improve the separation performance of polymer membrane. Few studies systematically investigated structure-property relationships in fluorinated polyimide structure. In this study, carboxylic groups are introduced into a fluorinated polyimide(6FDA-TFMB) via copolymerization with DABA diamine monomer. The hydrogen bond between –CF3 group in TFMB and –COOH group in DABA is proposed to enhance chain segment rigidity and optimize polymer chain arrangement. WAXD results and FFV data indicate that inter-chain cavity of fluorinated polyimide could be finely tuned by adjusting molar ratio of TFMB and DABA in the copolyimide. The resulted copolyimide membranes thus demonstrate tunable gas permeation properties. Gas permeability of 6FDA-TFMB/DABA firstly increases and then decreases, and ideal gas selectivity continuously increases with increasing DABA molar ratio. Among the polyimides, 6FDA-TFMB/DABA(6:4) membrane demonstrated superior separation performance, e.g. CO2 permeability of 135.6 Barrer and CO2/CH4 ideal selectivity of 31.6, surpassing the commercial cellulose acetate and Matrimid membrane. Attributed to the optimized interchain interaction, the 6FDA-TFMB/DABA (6:4) membrane displays an optimized CO2 plasticization resistance and physical aging in comparison with 6FDA-TFMB membranes. This study provides a guideline for controlling and optimize the performance of biphenyl fluorinated polyimide gas separation membrane.

Hydrogel Electrolyte with High Tolerance to a Wide Spectrum of pHs and Compressive Energy Storage Devices Based on It.

Normally, hydrogel electrolytes widely used in flexible energy storage devices have limited tolerance to different pHs. Most gel electrolytes will lose their compressible capability when the adaptable pH is changed. Herein, a poly(acrylamide3 -co-(sulfobetaine methacrylate)1 )@polyacrylamide (P(A3 -co-S1 )@PAM) hydrogel electrolyte equipped with a dual crosslinking network (DN) is successfully fabricated, which exhibits excellent tolerance to any pHs, endowing various energy storage devices including batteries and supercapacitors with superior mechanical durability. The batteries with mild and alkaline P(A3 -co-S1 )@PAM electrolytes display superior stability (over 3000 cycles). Additionally, a Zn||MnO2 battery based on the P(A3 -co-S1 )@PAM hydrogel electrolyte (mild) under 50% compression strain also shows excellent charge-discharge stability and high capacity at 152.4 mAh g-1 after 600 cycles. The strong reversible hydrogen bonds and electrostatic forces originating from zwitterionic structures of poly(sulfobetaine methacrylate) play an important role in dissipating and dispersing energy imposed abruptly. Meanwhile, the zwitterionic structure and intermolecular NH⋯OC hydrogen bonds of the hydrogel lead to the property of acid resistance and alkali resistance. The tough and robust covalent crosslinking bonds and the tight arrangement of DN polymer chains enable the hydrogel electrolytes to recover their initial shape fast once unloading.

Accumulation and ordering of P3HT oligomers at the liquid-vapor interface with implications for thin-film morphology.

The morphology of semiconducting polymer thin films is known to have a profound effect on their opto-electronic properties. Although considerable efforts have been made to control and understand the processes which influence the structures of these systems, it remains largely unclear what physical factors determine the arrangement of polymer chains in spin-cast films. Here, we investigate the role that the liquid-vapor interfaces in chlorobenzene solutions of poly(3-hexylthiophene) [P3HT] play in the conformational geometries adopted by the polymers. Using all-atom molecular dynamics (MD), and supported by toy-model simulations, we demonstrate that, with increasing concentration, P3HT oligomers in solution exhibit a strong propensity for the liquid-vapor interface. Due to the differential solubility of the backbone and side chains of the oligomers, in the vicinity of this interface, hexyl chains and the thiophene rings, have a clear orientational preference with respect to the liquid surface. At high concentrations, we additionally establish a substantial degree of inter-oligomer alignment and thiophene ring stacking near the interface. Our results broadly concur with the limited existing experimental evidence and we suggest that the interfacial structure can act as a template for film structure. We argue that the differences in solvent affinity of the side chain and backbone moieties are the driving force for the anisotropic orientations of the polymers near the interface. This finer grained description contrasts with the usual monolithic characterization of polymer units. Since this phenomenon can be controlled by concurrent chemical design and the choice of solvents, this work establishes a fabrication principle which may be useful to develop more highly functional polymer films.

Asymmetric Lumino-Transformer: Circularly Polarized Luminescence of Chiral Eu(III) Coordination Polymer with Phase-Transition Behavior.

A chiral Eu(III) coordination polymer with phase-transition behavior, [Eu(+tfc)3(m-dpeb)]n, (+tfc: (+)-3-trifluoroacetylcamphorato, m-dpeb: 1,3-bis(diphenylphosphorylethynyl)benzene) was reported for understanding the effect of polymer chain arrangement (orientation effect) on the circularly polarized luminescence (CPL) in a solid system. The phase-transition behavior of the transformable Eu(III) coordination polymer was characterized using differential scanning calorimetry and powder X-ray diffraction. The Eu(III) coordination polymer exhibited phase transition at approximately 180 °C. The magnitude of the CPL intensity was drastically changed because of the phase transition, without coordination geometrical change around the Eu(III) ion. In this study, the orientation effect of a chiral Eu(III) coordination polymer on the CPL properties in crystalline solid is demonstrated.

Li6.4La3Zr1.4Ta0.6O12/Star-Shaped Hybrid Polyhedral Oligomeric Cage Silsesquioxane Polymer Composite Electrolytes for All-Solid-State Lithium Metal Batteries

The low ionic conductivity and mechanical strength are important factors impeding the application of solid polymer electrolytes. Herein, we design synthesize an organic/inorganic hybrid star-shaped polymer of octa(poly(methyl methacrylate)–poly(poly(ethylene glycol) methyl ether methacrylate) cage oligomeric silsesquioxanes (POSS–(PMMA–PPEGMEM)8) by one-step free atom transfer radical polymerization (ATRP), and compound with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) to prepare a composite polymer electrolyte membrane (LP-CPEM). The star-shaped structure of the POSS–(PMMA–PPEGMEM)8 induced by octachloropropyl polyhedral cage oligomeric silsesquioxane (OCP-POSS) is beneficial to reduce the crystallinity of polymer and increase the movement of the polymer chain to form a continuous interconnected ion migration channel. The LLZTO fillers in the LP-CPEM could simultaneously hinder the orderly arrangement of polymer chains and provide other ion transport paths to increase the ion conductivity of LP-CPEM. The LP-CPEM with 7.5 wt % LLZTO has higher ionic conductivity of 3.8 × 10–4 S cm–1 at 30 °C and high mechanical strength (5.2 MPa). Additionally, Li/Li symmetric cells demonstrate stable constant current charging/discharging during 1000 h at 0.1 mA cm–2, and the all-solid-state batteries fabricated by the LP-CPEM exhibit good cyclic stability. It is promising for the development of next-generation high-safety all-solid-state lithium metal batteries.

Diversity of Coordination Architecture of Zinc Complexes with Diphenylarsinate

AbstractThe zinc complexes of diphenylarsinate [(Ph2AsO2)ZnCl] (1), [(Ph2AsO2)Zn(Ph2As(O)OH)Cl] (2) and [(Ph2AsO2)2Zn] (3) were prepared through the reaction of ZnCl2 with dihydroxodiphenylarsonium chloride [Ph2As(OH)2]Cl. Single‐crystal X‐ray diffraction analyses indicate that all three compounds form 1D polymer chain arrangements. Specifically, the [Ph2AsO2]− ligand coordinates with three Zn centres giving a syn,syn,anti μ3‐η1 : η2 mode in compound 1. A more diverse binding mode arised in compound 2: [Ph2AsO2]− shows a syn,anti μ2‐η1 : η1 bridging mode; while free ligand Ph2As(O)OH is bound to Zn through the oxygen atom of the As=O unit (monodentate). In addition, the hydrogen atom of Ph2As(O)OH forms a moderate hydrogen bond with the oxygen atom of [Ph2AsO2]−. Even though all [Ph2AsO2]− ligands also coordinate in a bridging mode in compound 3, a chain‐like arrangement with alternate single (anti,anti μ2‐η1 : η1) and triple (syn,syn μ2‐η1 : η1) bridging diphenylarsinate groups between tetrahedrally coordinated Zn atoms was identified.

DNA Origami Meets Polymers: A Powerful Tool for the Design of Defined Nanostructures.

The combination of DNA origami nanostructures and polymers provides a new possibility to access defined structures in the 100 nm range. In general, DNA origami serves as a versatile template for the highly specific arrangement of polymer chains. Polymer‐DNA hybrid nanostructures can either be created by growing the polymer from the DNA template or by attaching preformed polymers to the DNA scaffold. These conjugations can be of a covalent nature or be based on base‐pair hybridization between respectively modified polymers and DNA origami. Furthermore, the negatively charged DNA backbone permits interaction with positively charged polyelectrolytes to form stable complexes. The combination of polymers with tuneable characteristics and DNA origami allows the creation of a new class of hybrid materials, which could offer exciting applications for controlled energy transfer, nanoscale organic circuits, or the templated synthesis of nanopatterned polymeric structures.

Topochemical synthesis of different polymorphs of polymers as a paradigm for tuning properties of polymers

Different packing is a mechanism through which nature can produce materials of different properties from the same basic units. There is great interest in constructing different forms of the same polymer by utilising different packing. Common solution-synthesized polymers are amorphous and their post-synthesis crystallization into different topologies is almost impossible. Here we show solid-state polymerization of different reactive polymorphs of a monomer pre-organized in different topologies. Trimorphs of a dipeptide monomer pack in a head-to-tail fashion, placing the azide and alkyne of adjacent monomers in proximity. On heating, these crystals undergo a topochemical azide-alkyne cycloaddition reaction yielding triazole-linked polymer in three different crystalline states; one with antiparallel arrangement of polymer chains, another with parallelly oriented chains, and a third form containing a 1:1 blend of two different conformers aligned in parallel. This approach of exploiting different polymorphs of a monomer for topochemical polymerization to yield polymorphs of polymers is promising for future research.

Revealing the Aggregation Mechanism, Structure, and Internal Dynamics of Poly(vinyl alcohol) Microgel Prepared through Liquid–Liquid Phase Separation

The use of technologies based on soft polymer particles represents an effective way to deliver target molecules with a specific function. To design a well-performing delivery system, it is fundamental to rationalize both the aggregation and the structural properties of such particles. In this study, we present the kinetic and structural characterization over time of poly(vinyl alcohol) (PVA) microgels obtained through a salting-out process in the presence of NaCl. We have analyzed how both the polymer and salt concentrations affect the aggregation process. The aggregation rate as well as the morphology and physico-chemical parameters, such as mass and chain density of the microgels, have been determined through static and dynamic light scattering and discussed in the framework of the diffusion-limited and reaction-limited colloid aggregation. Insights into the polymer chain arrangements and their dynamics have been gained by means of small-angle neutron scattering and neutron spin-echo measurements. As a ...

Thermoresponsive Diblock Copolymer Films with a Linear Shrinkage Behavior and Its Potential Application in Temperature Sensors.

The linear shrinkage behavior in thermoresponsive diblock copolymer films and its potential application in temperature sensors are investigated. The copolymer is composed of two thermoresponsive blocks with different transition temperatures (TTs): di(ethylene glycol) methyl ether methacrylate (MEO2MA; TT1 = 25 °C) and poly(ethylene glycol) methyl ether methacrylate (OEGMA300; TT2 = 60 °C) with a molar ratio of 1:1. Aqueous solutions of PMEO2MA-b-POEGMA300 show a three-stage transition upon heating as seen with optical transmittance and small-angle X-ray scattering: dissolution (T < TT1), self-assembled micelles with core-shell structure (TT1 < T < TT2), and aggregation of collapsed micelles (T > TT2). Due to the restrictions in the polymer chain arrangement introduced by the solid Si substrate, spin-coated PMEO2MA-b-POEGMA300 films exhibit an entirely different internal structure and transition behavior. Neutron reflectivity shows the absence of an ordered structure normal to the Si substrate in as-prepared PMEO2MA-b-POEGMA300 films. After exposure to D2O vapor for 3 h and then increasing the temperature above its TT1 and TT2, the ordered structure is still not observed. Only a D2O enrichment layer is formed close to the hydrophilic Si substrate. Such PMEO2MA-b-POEGMA300 films show a linear shrinkage between TT1 and TT2 in a D2O vapor atmosphere. This special behavior can be attributed to the synergistic effect between the restrained collapse of the PMEO2MA blocks by the still swollen POEGMA300 blocks and the impedance of chain arrangement by the Si substrate. Based on this unique behavior, spin-coated PMEO2MA-b-POEGMA300 films are further prepared into a temperature sensor by implementing Ag electrodes. Its resistance decreases linearly with temperature between TT1 and TT2.

Modification of Oligo- and Polylactides With Macrocyclic Fragments: Synthesis and Properties.

Products of lactic acid polycondensation (poly- and oligolactic acids) are widely used as packaging materials, drug delivery agents, implants etc. Variety of their applications is caused by a number of practically important properties, e.g., biocompatibility and biodegradability, non-toxicity, and mechanical durability. Modification of these polymers with different additives allows improving their properties and extending future applications. In this manner, stability toward degradation, recognition of some substrates, extended thermal stability etc. can be improved. Macrocyclic compounds are promising candidates as modifiers. They are able to provide polymer materials with additional binding sites, impart certain orientation to spatial arrangement of polymer chains, change hydrophilic-lipophilic balance, and redox properties. The latter one can be used for assembling various electrochemical sensors and biosensors that combine steric discrimination of the analytes caused by oligolactides and highly sensitive response to their quantities caused by redox labels introduced. Different composite materials based on oligolactides as matrices for such redox labels were described in the assemblies of biosensors for drugs, pesticides, and antioxidants detection. In this mini-review, methods for the synthesis of the lactic acid oligomers and those modified with the macrocyclic fragments (porphyrin, cyclodextrin, and cyclophane) have been described. The effects of modifiers on complexation, thermal, and aggregation properties of materials are described. Analytical performance of oligolactide based sensors and biosensors has been considered with particular emphasis to the mechanism of signal generation.