Flexibility Of Polymer Backbone Research Articles

Combination of multivalent DR5 receptor clustering agonists and histone deacetylase inhibitors for treatment of colon cancer

Death Receptor 5 (DR5) targeted therapies offer significant promise due to their pivotal role in mediating the extrinsic pathway of apoptosis. Despite DR5 overexpression in various malignancies and the potential of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), clinical applications of anti-DR5 monoclonal antibodies (mAbs) have been hampered by suboptimal outcomes potentially due to lack of receptor clustering.To address the limitation, we developed N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-based conjugates integrating multiple copies of DR5-targeting peptide (cyclic WDCLDNRIGRRQCVKL; cDR5) to enhance receptor clustering and apoptosis. Three conjugates with variable number of cDR5 were prepared and denoted as PH-cDR5 (high valence), PM-cDR5 (medium valence) and PL-cDR5 (low valence). Our studies in TRAIL-sensitive and resistant cancer cell lines demonstrated that the HPMA copolymer-peptide conjugates (P-cDR5) significantly improved DR5 receptor clustering and induced apoptosis effectively. In TRAIL-sensitive colon cancer cells (COLO205, HCT-116), P-cDR5 showed efficacy comparable to anti-DR5 mAb Drozitumab (DRO), but P-cDR5 outperformed DRO in TRAIL-resistant cells (HT-29), highlighting the importance of efficient receptor clustering. In COLO205 cells PM-cDR5 exhibited an IC50 of 94 pM, while PH-cDR5 had an even lower IC50 of 15 pM (based on cDR5 equivalent concentration), indicating enhanced potency of the multivalent HPMA copolymer-based system with a flexible polymer backbone in comparison with the IC50 for TRAIL at 0.12 nM. Combining P-cDR5 with valproic acid, a histone deacetylase inhibitor, resulted in further enhancement of apoptosis inducing efficacy, along with destabilizing mitochondrial membranes and increased sensitivity of TRAIL-resistant cells. These findings suggest that attaching multiple cDR5 peptides to a flexible water-soluble polymer carrier not only overcomes the limitations of previous designs but also offers a promising avenue for treating resistant cancers, pointing toward the need for further preclinical exploration and validation of this innovative strategy.

Nanocomposites comprising PVA/CMC matrix and CNTs/Fe2O3 nanohybrid: A comparative investigation of structural, optical, electrical, and dielectric properties as an application in advanced electrochemical and optoelectronic devices

This work addresses the fabrication of innovative flexible polymer nanocomposite films for electrochemical products made of poly (vinyl alcohol) (PVA), carboxymethyl cellulose (CMC), multi-walled carbon nanotubes (CNTs), and hematite (α-Fe2O3) nanoparticles (NPs) as nanohybrid. The PVA/CMC-CNTs/Fe2O3 nanocomposite films were characterized using various approaches. The PVA/CMC blend polymer matrix shows significant improvements in terms of amorphous nature with the CNTs/Fe2O3 nanofiller content, resulting in an exceedingly flexible polymer backbone and with higher ionic conductivity of the PVA/CMC-CNTs/Fe2O3 nanocomposites films, as reported by the XRD examination. The nanoparticle surfaces and the blend matrix exhibit a significant interaction, as seen by the FTIR spectra. To learn more about how CNTs/Fe2O3 NPs affect the optical characteristics of the PVA/CMC, its optical characteristics were examined. The absorption edge appeared to migrate towards lower photon energy sides upon the addition of CNTs/Fe2O3 NPs to the PVA/CMC matrix. The Eg (direct and indirect) of pure PVA/CMC was considerably decreased from 5.12 to 3.55 eV and 4.23 to 3.01 eV respectively by adding 3.5 wt% of CNTs/Fe2O3 NPs. The results proved the influence of the nanofiller on the host polymer's decreased band gap energy. The blend nanocomposite had a substantially higher AC conductivity compared with the blend, and the PVA/CMC-3.5%CNTs/Fe2O3 nanocomposite had the highest electrical conductivity. It was discovered that while the dielectric loss and dielectric constant increased with the high content of nanoparticles, they reduced with increasing frequency. These findings demonstrated that the produced films had undergone substantial changes, which allows for the use of flexible films made of PVA/CMC-CNTs/Fe2O3 in a variety of electrochemical and optoelectronic applications.

Impact of Molecular-level Structural Disruption on Relaxation Dynamics of Polymers with End-on and Side-on Liquid Crystal Moieties.

In side-chain liquid crystal polymers (SCLCPs), short side chains are attached on a flexible polymer backbone, and each side chain can have a liquid crystal (LC) group attached at the final bead in either an end-on or a side-on configuration. SCLCPs with random sequences of end-on and side-on LC moieties exhibit nonmonotonic thermal behavior as a function of composition, with some mixed sequences having a lower isotropic to LC phase transition than either purely end-on or side-on configurations. The origin of this nonmonotonic thermal trend lies in the disruption of molecular-level positional ordering and alignment due to the different preferred types of ordering of the different LC attachment types. We compare coarse-grained molecular dynamics (MD) simulations and experiments on SCLCP systems with only one type of LC moiety and demonstrate qualitative agreement in the observed mesophases of end-on and side-on SCLCP systems. Specifically, end-on SCLCPs display a smectic B-like mesophase, with layers of polymer between LC layers, while side-on SCLCPs exhibit a quasi-hexagonal columnar structure of polymer and a nematic surrounding the LC mesophase. Detailed analysis of SCLCP systems with various compositions of these types of LC attachments via MD reveals structural disruption in systems with intermediate compositions. Simulation snapshots and anisotropy ratio measurements show how random SCLCP systems deviate from the expected behavior of prolate or oblate systems in terms of their conformation. This molecular disruption in random SCLCP systems, particularly with a high composition of side-on LC moieties, also significantly impacts the relaxation dynamics. Modifying the composition of the LC type of attachment (molecular structure) is a possible route to tuning both the phase behavior and mechanical response of these systems.

Influence of polymer amphiphilicity on the cyclization efficiency of poly(2-oxazoline)s

The steadily increasing interest in cyclic polymers has led to a plethora of proposed applications, particularly as biomaterials. However, the large-scale synthesis of cyclic polymers remains one of the greatest challenges in the field. One reason for this is the poorly understood role of the polymer structure on the cyclization efficiency, leading to synthesis protocols that must be optimized on a case-by-case basis without consideration for the chemical nature of the polymer. Recently, we found through a combination of laboratory experiments and molecular dynamics simulations that the polymer backbone flexibility has a major influence on the cyclization efficiency of poly(cyclic imino ether)s. Concurrently, we identified that a more flexible polymer backbone was also better solvated in the given organic solvent. To deconvolute the importance of the polymer backbone flexibility and solvation, in this study a variety of α-alkyne, ω-azide terminated (co)polymers of 2-ethyl-2-oxazoline and 2–n-butyl-2-oxazoline with different amphiphilicities, but the same polymer backbone, have been synthesized and subjected to copper-catalysed azide-alkyne cycloaddition (CuAAC) reactions in water. In agreement with our previous studies, it was observed that an increase in polymer chain hydrophobicity, and hence a decrease in solvation, leads to a significant decrease in cyclization efficiency. To further understand the effect of different CuAAC reaction conditions on the reaction outcome, different polymer concentrations and reaction temperatures were screened. This study highlights the importance of polymer amphiphilicity, and more generally solvation, in CuAAC protocols aimed towards the synthesis of cyclic polymers.

Synthesis, characterization, electrical, and magnetic properties of polyvinyl alcohol/carboxymethyl cellulose blend doped with nickel ferrites nanoparticles for magneto‐electronic devices

AbstractSolid polymer electrolytes are an intriguing technology in terms of magneto‐opto electronic applications due to having a high dielectric constant, a small band gap, and excellent magnetic characteristics. In order to improve structural, optical, dielectric, conductivity, and magnetic characteristics, this research seeks to prepare nickel ferrite (NiFe2O4) nanoparticles and polyvinylalcohol (PVA)/carboxymethyl cellulose (CMC) films containing NiFe2O4. Nanoparticles of NiFe2O4 are prepared using the co‐precipitation method. The CMC/PVA–NiFe2O4 nanocomposites films are prepared using casting solution. To improve their structural, optical, conductivity, dielectric, and magnetic characteristics, these films electrolytes were examined using XRD, TEM, FT‐IR, UV–vis, and VSM measurements. According to the XRD analysis, the CMC/PVA blend polymer matrix demonstrates a considerable increase in amorphous nature with the NiFe2O4 nanoparticles (NPs) content, producing a highly flexible polymer backbone, increasing ionic conductivity of the CMC/PVA–NiFe2O4 nanocomposite films. The complexation of dopant cations with the CMC/PVA polymer matrix's backbone is confirmed by the FT‐IR spectroscopy. According to the UV–visible technique, the dopant NiFe2O4 concentration considerably affects the optical energy band gap, and Urbach energy of the pure CMC/PVA. At higher loading, these effects are more pronounced. At room temperature, ac conductivity, the dielectric behavior, and electrical modulus formalism were studied. The blend's highest AC conductivity is 4.77 × 103 S/cm. After increasing the loading of NiFe2O4 to 1.5 wt%, it increased to 8.07 × 104 S/cm. There has also been research on dielectric permittivity and electric modulus to further understand conductivity relaxation and charge storage qualities. The polymer nanocomposite, generally, displayed better optical, dielectric constant, conductivity, and magnetic characteristics compared to pure CMC/PVA being useable in terms of high energy storage nanoelectronics' manufacturing.Highlights NiFe2O4 nanoparticles were prepared by using the co‐precipitation method. Nanocomposite films of CMC/PVA–NiFe2O4 were successfully prepared by casting method. XRD patterns confirmed the increase in the degree amorphousity for nanocomposites films compare pure blend. From optical energy gap results for samples prepared was enhanced after addition NiFe2O4. The dielectric and magnetic properties showed that all nanocomposites films exhibited enhanced as compared to pure CMC/PVA film.

Polyacrylate Backbone Promotes Photoinduced Reversible Solid-To-Liquid Transitions of Azobenzene-Containing Polymers

The development of polymers with efficient photoinduced reversible solid-to-liquid transitions is desirable for the design of healable materials, reconfigurable devices, and switchable adhesives. Herein, we demonstrate that an azobenzene-containing polyacrylate P-H exhibits more efficient photoinduced reversible solid-to-liquid transitions than its polymethacrylate analogue P-Me. The side chain of P-H or P-Me contains a hexamethylene spacer, a photoresponsive azobenzene group, and an n-decyl tail. Both P-H and P-Me show reversible cis–trans photoisomerization. Solid transP-H and P-Me change to liquid cis ones via UV-light-induced trans-to-cis isomerization; liquid cisP-H and P-Me revert to solid trans ones via visible-light-induced cis-to-trans back isomerization. Differential scanning calorimetry and rheology measurements revealed that photoinduced reversible solid-to-liquid transitions occur because P-H and P-Me have photoswitchable glass transition temperatures. Although P-Me exhibits a slightly faster rate for trans-to-cis photoisomerization than P-H due to fewer aggregates in solid state, cisP-H flows 20 times faster than cisP-Me because P-H has a more flexible polymer backbone. The low viscosity of cisP-H makes photoinduced solid-to-liquid transition efficient and enables the design of rapidly healable coatings. Our study shows that the design of a flexible backbone is a new strategy to develop rapidly healable polymers with more efficient photoinduced solid-to-liquid transitions.

Mechanically robust and highly conductive semi-interpenetrating network anion exchange membranes for fuel cell applications

A series of highly transparent semi-interpenetrating polymer network anion exchange membranes (SIPN AEMs) composed of a flexible and cation cross-linked polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (cQSEBS) component, and a rigid, highly-charged quaternized poly(2,6-dimethyl phenylene oxide) (QPPO) component are prepared. Flexible and rigid polymer backbones endow SIPN AEMs with excellent flexibility and mechanical strength. High charge content and well defined hydrophilic/hydrophobic phase separation patterns ensure SIPN AEMs with improved ionic conductivity. Alkali-resistant SEBS, enhanced dimensional stability and ordered microphase separation morphology contribute to the good chemical stability of SIPN-AEMs. Among these AEMs, SIPN-cQSEBS/QPPO-10 with an IEC of 1.93 mmol g−1 achieves a better trade-off between tensile strength (19.36 MPa at 25 °C in wet state), flexibility (58.43% at 25 °C in wet state) and OH− conductivity (103.1 mS cm−1 at 80 °C). Besides, SIPN-cQSEBS/QPPO-10 shows low swelling degree (15.4% at 80 °C) and high chemical stability (95.9%, 88.7%, 82.7% and 88.5% retention in weight, OH− conductivity, tensile strength and elongation at break, respectively, after immersing in 1 M NaOH at 80 °C for 30 days). Importantly, a fuel cell peak power density of 1.174 W cm−2 is obtained at 80 °C by using SIPN-cQSEBS/QPPO-10 as the separator.

A Molecular Shape Recognitive HPLC Stationary Phase Based on a Highly Ordered Amphiphilic Glutamide Molecular Gel.

Chiral glutamide-derived lipids form self-assembled fibrous molecular gels that can be used as HPLC organic phases. In this study, HPLC separation efficiency was improved through the addition of branched amphiphilic glutamide lipids to the side chains of a terminally immobilized flexible polymer backbone. Poly(4-vinylpyridine) with a trimethoxysilyl group at one end was grafted onto the surface of porous silica particles (Sil−VP15, polymerization degree = 15), and the pyridyl side chains were quaternized with a glutamide lipid having a bromide group (BrG). Elemental analysis indicated that the total amount of the organic phase of the prepared stationary phase (Sil−VPG15) was 38.0 wt%, and the quaternization degree of the pyridyl groups was determined to be 32.5%. Differential scanning calorimetric analysis of a methanol suspension of Sil−VPG15 indicated that the G moieties formed a highly ordered structure below the phase transition temperature even on the silica surface, and the ordered G moieties exhibited a gel-to-liquid crystalline phase transition. Compared with a commercially available octadecylated silica column, the Sil−VPG15 stationary phase showed high selectivity toward polycyclic aromatic hydrocarbons, and particularly excellent separations were obtained for geometrical and positional isomers. Sil−VPG15 also showed highly selective separation for phenol derivatives, and bio-related molecules containing phenolic groups such as steroids were successfully separated. These separation abilities are probably due to multiple interactions between the elutes and the highly ordered functional groups, such as the pyridinium and amide groups, on the highly ordered molecular gel having self-assembling G moieties.

Triphenylamine based redox-active, fluorescent polyamides: synthesis and photophysics

An electroactive series of polyamides was synthesized from 4,4′-diamino-4′′-phenoxy triphenylamine (1), 4,4′-diamino-4′′-benzyloxy triphenylamine (2) and terephthaloyl or isophthaloyl chloride. The FTIR (Fourier Transform Infrared) spectral characterization and solubility test of the subsequent polyamides (PA I-IV), UV-vis, photoluminescence spectral analysis (PL) and cyclic voltammetry were utilized to assess photophysical and electrochemical properties of the materials. The oxidative-thermal stability of the polyamides as judged by thermogravimetric analysis was found to be in the range 438-532 °C with the char yield more than 53% at 800 °C. Introduction of aryloxy triphenylamine units along with polymer backbone flexibility improved the organosolubility of the synthesized polyamides (PA I-IV). The appreciable organosolubility of the (PA I-IV) is enough to be used in coating applications such as inkjet printing. Bluish green light emission from our synthesized materials upon excitation at 375 nm is credited to the triphenylamine linked amide-based polymer chain. Both pendent phenoxy and benzyloxy groups at para position in (PA I-IV) have also elevated the HOMO energy levels and hence lowered the onset oxidation potential. Additionally, the computational analysis was also conducted to get optimized ground-state geometry by DFT method (B3LYP) with 6-31G basis set. The 3-dimensional distributions of both HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) of the polymers were obtained. The computational data of the polymers also augmented the experimental data suggesting their future use as redox-active materials.

Conformational Stability Effect of Polymeric Iron Chelators.

SummaryThe design and synthesis of metal chelators with extraordinary metal affinities is a basic and challenging scientific problem of both fundamental and practical importance. Here, we demonstrate a “conformational stability effect” that can significantly enhance the metal affinity of ligands after conjugation to polymer chains with the ability to spontaneously adopt a specific conformation as an optimal “soft” scaffold to ensure maximum thermodynamic stability of the metal complexes. Using iron chelators as models, we show that simple conjugation of small molecule catechol ligands to a polyallylamine chain resulted in more than 8–9 orders of magnitude enhancement of the iron-binding affinity, which is comparable to that of enterobactin, the strongest iron chelator ever known. This study demonstrates that flexible polymer chelators may realize the highest possible metal affinities of the conjugated ligands owing to their ability to achieve an optimal conformation, which could advance the identification of strong metal chelators.

Dual-Functional Polymer Binders for Silicon Based Electrodes

As the “inert” materials in electrode, polymer binders play an important role in the long-term performance of silicon-based electrode. Several principles have been recognized to fabricate a “better” binder, there continues to be a lack of a rational design that would meet the robust criteria required for silicon (Si) anodes. Herein, we will present a synthetic polymer binder, i.e., catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA) that will serve both wetness-resistant adhesion capability via catechol grafting and mechanical robustness via in-situ formation of a three-dimensional (3D) network. The SiNPs based anode with the designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). Properties which are traditionally considered to be advantageous, including stronger adhesion strength and higher mechanical robustness, do not always improve the binder performance. A semi-quantitative analysis on the main-chain scaling behavior and stiffness also demonstrated that both catechol grafting and crosslinking lead to the reduced flexibility of polymer backbone for the resultant binder system. It turns out that the end-to-end distance of the two adjacent crosslinking points (Re) should be no less than the persistence length (lp) of the chitosan backbone for an efficient binding performance. The relationship established between binder properties and electrochemical performance of consequent Si electrode is imperative for designing polymer binders with optimized electrochemical performance. The strategy of in-situ construction of a functional polymer network is instructive for the design of high-performance polymer binders not only for Si based anodes, but also for a wide variety of other types of alloy and conversion-based electrodes. Figure 1

Design of Mechanically Robust Polymer Membranes for Non-Aqueous Flow Battery

Large scale grid storage is imperative for an efficient use of renewable energies. While aqueous redox flow batteries (RFBs) such as a vanadium-based aqueous RFB are relatively mature technologies for a grid storage, non-aqueous RFBs present an attractive alternative strategy for potentially providing much higher energy density. One of the key enablers for non-aqueous RFBs is mechanically robust and highly ion-conductive membranes. In aqueous RFBs, membranes can achieve high proton or anion conductivity due to water mediating their ion conduction, thus there are various high performance membranes for aqueous RFBs. On the other hand, for membranes in non-aqueous RFBs, achieving high ion conductivity while maintaining mechanical and chemical stability is a major challenge. The design principle for such membranes is poorly understood due to the complexity of the system. Our membranes are developed for a non-aqueous RFB with an alkali alloy anode technology that has the potential to achieve high energy density, high safety, low cost and long cycle life. This presentation will discuss the fundamental design principle in polymer membranes for non-aqueous RFBs and our recent efforts on the development of novel plasticized polymer membranes that simultaneously provide high conductivity and tailored mechanical modulus. In this study, mechanically robust crosslinked poly(ethylene oxide) membranes were synthesized and doped with sodium triflate and tetraglyme. The relationships between ion conductivity (reached up to 10-4-10-3 S/cm at r.t.), salt/gel content, glass transition temperature (Tg) and mechanical properties are investigated. The synthesized membranes are mechanically robust with storage modulus maintaining at ~1 MPa from -20 °C to 180 °C even saturated with tetraglyme. Furthermore, mechanically tailored novel single-ion conducting polymer electrolytes (SICPEs); block and graft copolymers of poly[(4-styrenesulfonyl) (trifluromethane-sulfonyl)imide] (poly(STF)) and poly[1-[3-(methacryloyloxy)-propylsulfonyl]-1-(trifluoromethanesulfonyl)imide] (poly(MPA)), were investigated. The SICPEs were synthesized by covalently attaching anionic moieties to the polymer backbones that only allows specific cations, such as lithium or sodium ions, to move freely and provide ionic conductivity (i.e. the transference number is close to 1) which is imperative for RFBs. These novel SCPE membranes include a membrane with a flexible polymer backbone to afford mechanical robustness and stretchability, and poly(STF) or poly(MPA) as side chains to provide single-ion conductivity. The effect of monomer type, degree of polymerization of the side chain, and different cations are also studied. The obtained polymer membrane showed 100% elongation and around 10-4 S/cm single-ion conductivity (no salt) at 30 °C after being doped with propylene carbonate. This work is funded by Dr. Imre Gyuk, Office of Electricity Delivery and Reliability, Department of Energy and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC.

Synthesis, mechanical properties and biodegradation of various acrylic acid-grafted poly(butylene succinate-co-terephthalate)/organically modified layered zinc phenylphosphonate nanocomposites

A new series of biodegradable aliphatic-aromatic nanocomposites containing various acrylic acid-grafted poly(butylene succinate-co-terephthalate) (PBST) and organically modified layered zinc phenylphosphonate (m-PPZn) were successfully synthesized through the transesterification and polycondensation having the covalent linkages between polymer and inorganic materials. Fourier transform infrared (FTIR) and 13C-nuclear magnetic resonance (NMR) spectra demonstrate the successful grafting of acrylic acid to PBST (g-PBST). Both wide-angle X-ray diffraction and transmission electron microscopy data show that the g-PBST polymer matrix was intercalated into the interlayer spacing of m-PPZn. The additional m-PPZn into g-PBST matrix significantly enhanced the storage modulus as compared with that of neat g-PBST. The reduction in thermal stability was observed in all g-PBST/m-PPZn systems, which is probably caused by more nucleation to form more tiny and imperfect crystals. The biodegradations of neat g-PBST copolymers and g-PBST/m-PPZn nanocomposites were investigated using lipase from Pseudomonas sp. The degradation rates of the neat g-PBST copolymers increased in the order of g-PBST-70 > g-PBST-50 > g-PBST-30. The faster degradation rate of g-PBST-70 is a result of a higher content of succinic acid unit and chain flexibility of polymer backbone. Furthermore, the weight loss increased by increasing the loading of m-PPZn, suggesting that the existence of m-PPZn improved the degradation of the g-PBST copolymers.

Glycopolymers Mimicking GM1 Gangliosides: Cooperativity of Galactose and Neuraminic Acid for Cholera Toxin Recognition.

Glycopolymers mimicking GM1 gangliosides were synthesized by incorporating multiple types of carbohydrates into the polymer backbone. The glycopolymers were immobilized onto gold surfaces, and the interactions with the cholera toxin B subunit (CTB) were analyzed using surface plasmon resonance imaging. The glycopolymer containing both galactose and neuraminic acid showed enhanced recognition of CTB. The interaction was enhanced mainly because of an improvement in the dissociation process by the binding of the neuraminic acid group in the GM1 binding pocket. This cooperativity of galactose and neuraminic acid was achieved by incorporation into the same flexible polymer backbone, and the importance of the close placement of galactose and neuraminic acid groups was revealed. These results will be valuable in medical fields and also for the development of biofunctional materials.

Effect of polymer backbone flexibility on blue phase liquid crystal stabilization

In this study, we synthesized two novel monofunctional acrylate monomers A0DA and A3DA featuring a benzene core and a dodecyl tail, and then investigated their effect on blue phase liquid crystal (BPLC) stabilization. The benzene core is directly linked to the acrylate unit in A0DA, which forms a rigid polymeric backbone. Whereas in A3DA,a propyl spacer is employed to separate the benzene unit from the acrylate group, thereby allowing backbone mobility. By using A0DA as a monofunctional monomer in the BPLC precursor composite, stabilization of BPLC was not seen upon photopolymerization. Interestingly, the use of A3DA showed successful stabilization of BPI lattice structure after polymerization. These results confirm that the origin of stabilization effect of blue phase is the flexibility of A3DA backbone employed; therefore, the polymeric backbone flexibility is suggested to have a major influence on BP stabilization process. Furthermore, we demonstrated a low voltage electro-optical switching of PS-BPLC built on A3DA, while preserving other desirable properties of BPLC. The present study provides useful insight into monomer designs towards BPLC stabilization and enhancement of electro-optical performance.

Microphase separation and mechanical performance of thermoplastic elastomers based on poly(glycidyl azide)/poly(oxytetramethylene glycol)

To improve the mechanical performance of poly(glycidyl azide) (GAP)‐based thermoplastic elastomers (TPEs), poly(oxytetramethylene glycol) (PTMG) which has flexible polymer backbone was introduced into their chemical structure by polyaddition. The effects of crystalline PTMG segment on the macro morphology, microphase separation, local hydrogen bonding, and mechanical performance of GAP‐based TPEs were investigated. These obtained elastomers have a transparent and homogeneous phase structure, indicating that no macroscopic phase separation occurred. Meanwhile, the small‐angle X‐ray scattering (SAXS) demonstrated that the long‐range ordered microstructures formed by the crystallization of flexible PTMG segments was existed in the elastomers and the phase separated microstructure was enhanced with increasing the content of PTMG. These results were also confirmed by the investigation of crystalline behavior by wide‐angle X‐ray diffraction (WAXD) and loss factor curves by dynamic mechanical analyzer (DMA). The enhancement of microphase separated structure leads to the significant improvement of tensile properties, modulus, and creep resistance. These GAP/PTMG‐based TPEs with enhanced mechanical performance imply potential applications in propellant formulations. POLYM. ENG. SCI., 58:E167–E173, 2018. © 2018 Society of Plastics Engineers

Effect of Chain Flexibility and Interlayer Interactions on the Local Dynamics of Layered Polymer Systems

Layered polymeric systems are widely used in membrane separation applications; chain mobility in these layered systems is a key consideration in the design of the membranes. The transport properties of membrane polymers can be significantly altered by the perturbations in chain dynamics induced by the presence of an interface and also by the topological properties of the polymers constituting the layered systems. In this work, we use molecular dynamics (MD) simulations to determine the effects of polymer backbone flexibility and interlayer interactions on the glass transition and chain dynamics of polymer layers in the layered systems. We observed that the onset of glass transition of the entire layered system is governed by the stiffer polymer layer and is independent of the type of interactions between the layers. However, the interlayer interactions govern the strength of the glass transition of the entire layered system. Polymer mobility, on the other hand, exhibits a strong dependence on both the cha...

Single Chain Polymeric Nanoparticles to Promote Selective Hydroxylation Reactions of Phenol Catalyzed by Copper.

Metal-containing single chain polymeric nanoparticles (SCPNs) can be used as synthetic mimics of metalloenzymes. Currently, the role of the folded polymer backbones on the activity and selectivity of metal sites is not clear. Herein, we report our findings on how polymeric frameworks modulate the coordination of Cu sites and the catalytic activity/selectivity of Cu-containing SCPNs mimicking monophenol hydroxylation reactions. Imidazole-functionalized copolymers of poly(methyl methacrylate-co-3-imidazolyl-2-hydroxy propyl methacrylate) were used for intramolecular Cu-imidazole binding that triggered the self-folding of polymers. Polymer chains imposed steric hindrance which yielded unsaturated Cu sites with an average coordination number of 3.3. Cu-containing SCPNs showed a high selectivity for the hydroxylation reaction of phenol to catechol, >80%, with a turnover frequency of >870 h-1 at 60 °C. The selectivity was largely influenced by the flexibility of the folded polymer backbone where a more flexible polymer backbone allows the cooperative catalysis of two Cu sites. The second coordination sphere provided by the folded polymer that has been less studied is therefore critical in the design of active mimics of metalloenzymes.

Absence of conformational change in complement factor 3 and factor XII adsorbed to acrylate polymers is related to a high degree of polymer backbone flexibility.

In previous investigations, the authors have examined the adsorption of albumin, immunoglobulin, and fibrinogen to a series of acrylate polymers with different backbone and side-group flexibility. The authors showed that protein adsorption to acrylates with high flexibility, such as poly(lauryl methacrylate) (PLMA), tends to preserve native conformation. In the present study, the authors have continued this work by examining the conformational changes that occur during the binding of complement factor 3 (C3) and coagulation factor XII (FXII). Native C3 adsorbed readily to all solid surfaces tested, including a series of acrylate surfaces of varying backbone flexibility. However, a monoclonal antibody recognizing a "hidden" epitope of C3 (only exposed during C3 activation or denaturation) bound to the C3 on the rigid acrylate surfaces or on polystyrene (also rigid), but not to C3 on the flexible PLMA, indicating that varying degrees of conformational change had occurred with binding to different surfaces. Similarly, FXII was activated only on the rigid poly(butyl methacrylate) surface, as assessed by the formation of FXIIa-antithrombin (AT) complexes; in contrast, it remained in its native form on the flexible PLMA surface. The authors also found that water wettability hysteresis, defined as the difference between the advancing and receding contact angles, was highest for the PLMA surface, indicating that a dynamic change in the interface polymer structure may help protect the adsorbed protein from conformational changes and denaturation.

Molecular Dynamics of Multivalent Soluble Antigen Arrays Support a Two-Signal Co-delivery Mechanism in the Treatment of Experimental Autoimmune Encephalomyelitis.

Many current therapies for autoimmune diseases such as multiple sclerosis (MS) result in global immunosuppression, rendering insufficient efficacy with increased risk of adverse side effects. Multivalent soluble antigen arrays, nanomaterials presenting both autoantigen and secondary inhibitory signals on a flexible polymer backbone, are hypothesized to shift the immune response toward selective autoantigenic tolerance to repress autoimmune disease. Two-signal co-delivery of both autoantigen and secondary signal were deemed necessary for therapeutic efficacy against experimental autoimmune encephalomyelitis, a murine model of MS. Dynamic light scattering and in silico molecular dynamics simulations complemented these studies to illuminate the role of two-signal co-delivery in determining therapeutic potential. Physicochemical characteristics such as particle size and molecular affinity for intermolecular interactions and chain entanglement likely facilitated cotransport of two signals to produce efficacy. These findings elucidate potential mechanisms whereby soluble antigen arrays enact their therapeutic effect and help to guide the development of future multivalent antigen-specific immunotherapies.