Random Polymer Research Articles

Synthetic Random Copolymers as a Molecular Platform To Mimic Host-Defense Antimicrobial Peptides.

Synthetic polymers have been used as a molecular platform to develop host-defense antimicrobial peptide (AMP) mimetics which are effective in killing drug-resistant bacteria. In this topical review, we will discuss the AMP-mimetic design and chemical optimization strategies as well as the biological and biophysical implications of AMP mimicry by synthetic polymers. Traditionally, synthetic polymers have been used as a chemical means to replicate the chemical functionalities and physicochemical properties of AMPs (e.g., cationic charge, hydrophobicity) to recapitulate their mode of action. However, we propose a new perception that AMP-mimetic polymers are an inherently bioactive platform as whole molecules, which mimic more than the side chain functionalities of AMPs. The tunable nature and chemical simplicity of synthetic random polymers facilitate the development of potent, cost-effective, broad-spectrum antimicrobials. The polymer-based approach offers the potential for many antimicrobial applications to be used directly in solution or attached to surfaces to fight against drug-resistant bacteria.

An invariance principle for the two-dimensional parabolic Anderson model with small potential

We prove an invariance principle for the two-dimensional lattice parabolic Anderson model with small potential. As applications we deduce a Donsker type convergence result for a discrete random polymer measure, as well as a universality result for the spectrum of discrete random Schrodinger operators on large boxes with small potentials. Our proof is based on paracontrolled distributions and some basic results for multiple stochastic integrals of discrete martingales.

Optically active tyrosine‐containing poly(N‐propargylamides): Synthesis, helical conformation, and infrared emissivity study

ABSTRACTNovel optically active and racemic poly(N‐propargylamides) bearing tyrosine pendants (LPT, DPT, and RPT) were synthesized and characterized. The polymers possessed moderate molecular weights and were thoroughly soluble in common organic solvents. The secondary structure of these three polymers in chloroform was studied and the results indicated that LPT and DPT could adopt helical structures with predominantly one‐handed screw sense according to their intense Cotton effect and large specific rotation values, while RPT adopted random coiled polymer chain. The amide groups could form amide‐amide hydrogen bonds to engender the twist of dihedral angle and the strong steric repulsion of phenol groups might have the opposite effect on the helix. The helical structure of the optically active polymers were conclusively constructed and stabilized by the optimization of intra‐ and intermolecular hydrogen bonding and steric repulsion of the side chains. Moreover, the infrared emissivity values of LPT and DPT at 30 °C were 0.682 and 0.671, which were much lower than RPT. LPT and DPT also showed superior heat resistance due to their unique helical conformation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44824.

A random donor polymer based on an asymmetric building block to tune the morphology of non-fullerene organic solar cells

The introduction of an asymmetric unit enables a fine-tuned morphology and thus up to 10.4% efficiency for non-fullerene organic solar cells.

Random D–A1–D–A2terpolymers based on benzodithiophene, thiadiazole[3,4-e]isoindole-5,7-dione and thieno[3,4-c]pyrrole-4,6-dione for efficient polymer solar cells

New efficient D–A1–D–A2random terpolymers for photovoltaic applications.

$q$-randomized Robinson–Schensted–Knuth correspondences and random polymers

We introduce and study q -randomized Robinson–Schensted–Knuth (RSK) correspondences which interpolate between the classical ( q=0 ) and geometric q \nearrow1 ) RSK correspondences (the latter ones are sometimes also called tropical). For 0<q<1 our correspondences are randomized, i.e., the result of an insertion is a certain probability distribution on semistandard Young tableaux. Because of this randomness, we use the language of discrete time Markov dynamics on two-dimensional interlacing particle arrays (these arrays are in a natural bijection with semistandard tableaux). Our dynamics act nicely on a certain class of probability measures on arrays, namely, on q -Whittaker processes (which are t=0 versions of Macdonald processes of Borodin–Corwin [8]). We present four Markov dynamics which for q=0 reduce to the classical row or column RSK correspondences applied to a random input matrix with independent geometric or Bernoulli entries. Our new two-dimensional discrete time dynamics generalize and extend several known constructions. (1) The discrete time q -TASEPs studied by Borodin–Corwin [7] arise as one-dimensional marginals of our „column" dynamics. In a similar way, our“row" dynamics lead to discrete time q -PushTASEPs – new integrable particle systems in the Kardar–Parisi–Zhang universality class. We employ these new one-dimensional discrete time systems to establish a Fredholm determinantal formula for the two-sided continuous time q -PushASEP conjectured by Corwin–Petrov [23]. (2) In a certain Poisson-type limit (from discrete to continuous time), our two-dimensional dynamics reduce to the q -randomized column and row Robinson–Schensted correspondences introduced by O’Connell–Pei [59] and Borodin–Petrov [15], respectively. (3) In a scaling limit as q\nearrow1 , two of our four dynamics on interlacing arrays turn into the geometric RSK correspondences associated with log-Gamma (introduced by Seppäläinen [70] or strict-weak (introduced independently by O’Connell–Ortmann [58] and Corwin–Seppäläinen–Shen [25] directed random lattice polymers.

Could a Proto-Ribosome Emerge Spontaneously in the Prebiotic World?

An indispensable prerequisite for establishing a scenario of life emerging by natural processes is the requirement that the first simple proto-molecules could have had a realistic probability of self-assembly from random molecular polymers in the prebiotic world. The vestige of the proto-ribosome, which is believed to be still embedded in the contemporary ribosome, is used to assess the feasibility of such spontaneous emergence. Three concentric structural elements of different magnitudes, having a dimeric nature derived from the symmetrical region of the ribosomal large subunit, were suggested to constitute the vestige of the proto-ribosome. It is assumed to have materialized spontaneously in the prebiotic world, catalyzing non-coded peptide bond formation and simple elongation. Probabilistic and energetic considerations are applied in order to evaluate the suitability of the three contenders for being the initial proto-ribosome. The analysis points to the simplest proto-ribosome, comprised of a dimer of tRNA-like molecules presently embedded in the core of the symmetrical region, as the only one having a realistic statistical likelihood of spontaneous emergence from random RNA chains. Hence it offers a feasible starting point for a continuous evolutionary path from the prebiotic matter, through natural processes, into the intricate modern translation system.

Damage assessment of random multiwalled carbon nanotube-reinforced polymer nanocomposites

Abstract The paper presents a numerical procedure to evaluate the mechanical properties and predict the damage initiation of random multiwalled carbon nanotube-reinforced polymer nanocomposites (MWCNT-RPNC). The Hashin-Shtrikman (H-S) random prediction model is used to compute the properties of the reinforced polymer matrix, whereas the Chamis model is used to compute the lamina properties and the Hashin progressive damage model within the ABAQUS environment is used as a finite element analysis (FEA) tool to predict the damage initiation in the reinforced composite material. Experimental testing is employed to validate the numerical results and to adjust the H-S prediction model for MWCNT-RPNC.

Polymer Topology Driven Enzymatic Biodegradation in Polycaprolactone Block and Random Copolymer Architectures for Drug Delivery to Cancer Cells

The present investigation reports polymer topology design principle for programming the enzymatic biodegradation and delivery of anticancer drugs at the intracellular compartments of breast and cervical cancers. To accomplish this goal, new classes of biodegradable amphiphilic block and random copolymers based on hydrophilic carboxylic-functionalized polycaprolactone (CPCL) and hydrophobic polycaprolactone (PCL) units were designed via ring-opening polymerization methodology. The interchain interactions and their packing were directly controlled by the topology of the polymers, and the block copolymers were found to be as semicrystalline materials. These amphiphilic block and random polymers were readily dispersible in water, and they self-assembled into <200 nm nanoparticles. These nanoparticles exhibited excellent capability for loading anticancer drug doxorubicin (DOX) in the hydrophobic pocket. In vitro drug release kinetics revealed that the polymer nanoscaffolds were stable under physiological condi...

Block Copolymer Sdapp Membranes for Vanadium Redox Flow Batteries-Strategy to Address Transport and Durability

The electrolyte separator (membrane) is a key component in vanadium redox flow batteries (VRFB) for large scale electrical energy storage. In the VRFB cell, the separator serves to physically separate positive and negative electrolyte solutions while establishing ionic conduction to pass current between two half cells. High ionic conductivity, low vanadium permeability, chemical stability and low cost are desired properties of RFB separators. To serve as a separator, the membrane should deter unwanted redox species transport while maintaining excellent ionic transport properties to minimize ohmic resistance. In the harsh electrolyte environment, the membrane must be stable enough to withstand chemical attacks in the electrolyte environment for a long lifespan. Moreover, the cost of the separator must be kept low enough to be integrated into large-scale battery system. Generally, ion exchange membranes are used as electrolyte separator in VRFBs. Sulfonated Diels Alder poly(phenylene) (SDAPP) cation exchange membranes have emerged as a good membrane candidate for both proton exchange membrane fuel cell and VRFB. The first generation SDAPP is a partially sulfonated poly(phenylene) random polymer. The random SDAPP membrane has shown comparable performance to Nafion in transport study and battery testing.1 From the perspective transport properties, SDAPP is satisfactory as anelectrolyte separator in VRFBs. However, random SDAPP is not chemically stable enough in the electrolyte environment to serve for a targeted lifespan because the unfunctionalized benzene ring in SDAPP is vulnerable to attack from V5+ (VO2 +) ion, a strong oxidant. Sulfonated polyphenylene/polysulfone block copolymer SDAPP membranes show significantly improved resistance to V5+ attack and excellent cell performance.2 The SDAPP block copolymer consists of a hydrophilic segment of fully sulfonated polyphenylene and hydrophobic segment of polysulfone. The block-SDAPP membrane provides an extended lifespan within VRFB environment in comparison to random SDAPP. Chemical stability of block-SDAPP is enhanced by full sulfonation of poly(phenylene) in the hydrophilic segment. Ionic conductivity is not sacrificed by block copolymerization. In the battery, the performance of block-SDAPP can be better than state of art Nafion 212. As is shown in the figure, at 500 mA/cm2cycling current density, cells equipped with three different block-SDAPP membranes can reach 76% energy efficiency, compared to 70% with Nafion 212, with the same electrode and electrolyte conditions. About 80% voltage efficiency was achieved with block-SDAPP membranes, because of the lowered internal resistance. Moreover, the coulombic efficiency reached by the three block SDAPPs is respectively 97%, 95% and 93%, compared to 95% of Nafion. Vanadium crossover across block SDAPP membranes is similar to that in Nafion 212. Considering that block-SDAPPs have lower ASR in the battery, the ionic selectivity of block SDAPP is essentially better than Nafion. To further optimize the structure of block-SDAPP for VRFB application, we are investigating the correlation between structure and performance of block-SDAPP. Under battery electrolyte conditions, ionic equilibrium, ionic transport and membrane morphology will be studied via the protocol established in previous studies.3Sulfuric acid, water uptake and vanadium ion partitioning in membrane will be determined after being equilibrated in electrolyte of various acid and vanadium composition to simulate battery environment. Conductivity and vanadium permeability of block SDAPP will also be measured after the same equilibration. Since water is a critical mediator for proton and cation transport in aqueous media, pulsed field gradient nuclear magnetic resonance (PFG-NMR) will be performed to investigate proton and vanadium transport mechanisms in equilibrated membranes. Membrane morphology will be studied by transmission electron microscopy and small angle X-ray scattering will be used to establish the geometry of ionic cluster channel. Acknowledgement This work is supported by Dr. Imre Gyuk, Office of Electricity Delivery and Energy Reliability, US Department of Energy.

Novel regular D–A-conjugated polymers based on 2,6-bis(6-fluoro-2-hexyl-2H-benzotriazol-4-yl)-4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene derivatives: Synthesis, optoelectronic, and electrochemical properties

Regioregular (P1) and random (P2) polymers were prepared by the reaction of equimolar amounts of dibromides M2 or M3 with bis(stannyl) monomer M1. The regioregularity of the conjugated chain in P1 was shown to affect considerably its optical properties. The HOMO/LUMO values and electrochemical band gap for polymers P1 or P2 found by cyclic voltammetry are–5.40/–3.40,–5.31/–3.33, and 2.00/1.96 eV, respectively. The LUMO levels for P1 and P2 are located higher than for PC71BM (–4.3 eV) by 0.84 and 0.97 eV, respectively. The low-lying HOMO levels of P1 and P2 are favorable for the high value of open-circuit voltage and make these polymers attractable candidates for polymer solar cells.

Effect of substituent groups on quinoxaline-based random copolymers on the optoelectronic and photovoltaic properties

Abstract In this study, three low band gap donor-acceptor (D-A) type quinoxaline-based random copolymers were synthesized. The effect of varying substituent groups on quinoxaline groups on optoelectronic properties and the performance of bulk-heterojunction polymer solar cells was investigated. Electrochemical and optical studies indicate that these copolymers are promising materials for both electrochromic and polymer solar cells applications. Two random polymers were found as excellent candidates for NIR electrochromic devices owing to their 60% and 94% optical contrast values respectively in NIR region with less than 1 s switching times. Polymer solar cells were constructed using the copolymers as the donor components together with PC71BM as the acceptor in the active layer. Among all, the highest PCE was reported as 2.13%.

High Performance All-Polymer Solar Cells by Synergistic Effects of Fine-Tuned Crystallinity and Solvent Annealing.

Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally <0.65), which is strongly correlated with the mobility and film morphology of polymer:polymer blends. In this work, we find a facile method to modulate the crystallinity of the well-known naphthalene diimide (NDI) based polymer N2200, by replacing a certain amount of bithiophene (2T) units in the N2200 backbone by single thiophene (T) units and synthesizing a series of random polymers PNDI-Tx, where x is the percentage of the single T. The acceptor PNDI-T10 is properly miscible with the low band gap donor polymer PTB7-Th, and the nanostructured blend promotes efficient exciton dissociation and charge transport. Solvent annealing (SA) enables higher hole and electron mobilities, and further suppresses the bimolecular recombination. As expected, the PTB7-Th:PNDI-T10 solar cells attain a high PCE of 7.6%, which is a 2-fold increase compared to that of PTB7-Th:N2200 solar cells. The FF of 0.71 reaches the highest value among all-PSCs to date. Our work demonstrates a rational design for fine-tuned crystallinity of polymer acceptors, and reveals the high potential of all-PSCs through structure and morphology engineering of semicrystalline polymer:polymer blends.

Surface Energy Modification of Semi-Random P3HTT-DPP.

Alkyl solubilizing side chains on conjugated polymers can serve as a handle for modifying polymer properties. Recently, oligo-ether and semifluoro alkyl side chains were utilized to tune the surface energy of random P3HT-based polymers without changing the optical and electronic properties. Here, this method is applied to semi-random poly(3-hexylthiophene-thiophene-diketopyrrolopyrrole) (P3HTT-DPP) and the subsequent polymer device, optical, electronic, structural, and thermal properties are characterized. P3HTMETT-DPP, bearing oligo-ether side chains, exhibited higher crystallinity, closer lamellar packing, and lower temperature thermal transitions. P3HTFHTT-DPP, featuring semifluoro alkyl side chains, presented reduced crystallinity, greater lamellar packing distances, and higher temperature thermal transitions. P3HTMETT-DPP performed similarly to P3HTT-DPP under identical processing conditions, whereas P3HTFHTT-DPP had greatly reduced JSC due to lower polymer concentration necessitated by solubility.

A Generalized Variational Principle for Gaussian Random Fields

The freezing property for a family of models involving Gaussian Random Fields is studied in a unified manner and it is related to the behaviour of the entropy of the Gibbs measure in terms of the variational principle. The analysis includes the Gaussian Multiplicative Chaos, Random Energy Model, Spin Glass Mean-Field, and the Random Polymers models.

Controlled variation of monomer sequence distribution in the synthesis of aromatic poly(ether ketone)s

The effects of varying the alkali metal cation in the high-temperature nucleophilic synthesis of a semi-crystalline, aromatic poly(ether ketone) have been systematically investigated, and striking variations in the sequence distributions and thermal characteristics of the resulting polymers were found. Polycondensation of 4,4′-dihydroxybenzophenone with 1,3-bis(4-fluorobenzoyl)benzene in diphenylsulphone as solvent, in the presence of an alkali metal carbonate M2CO3 ( M = Li, Na, K, or Rb) as base, affords a range of different polymers that vary in the distribution pattern of two-ring and three-ring monomer units along the chain. Lithium carbonate gives an essentially alternating and highly crystalline polymer, but the degree of sequence randomization increases progressively as the alkali metal series is descended, with rubidium carbonate giving a fully random and non-thermally crystallizable polymer. Randomization during polycondensation is shown to result from reversible cleavage of the ether linkages in the polymer by fluoride ions, and an isolated sample of alternating sequence polymer is thus converted to a fully randomized material on heating with rubidium fluoride.

On two-time distribution functions in (1 + 1) random directed polymers

An asymptotic analytic expression for the two-time free energy distribution function in (1 + 1) random directed polymers is derived in the limit when the two times are close to each other.

Polarized random laser emission from an oriented disorder polymer optical fiber

We demonstrate the realization of a polarized random polymer fiber laser (RPFL) in the different disordered gain media doped polymer optical fibers (POFs). Multiple scattering of disordered media in the orientated POF was experimentally verified to account for polarized lasing observed in our RPFL system. This Letter presents a new avenue for fabricating polarized RPFLs in a large scale. Meanwhile, the polarization-maintaining property of random lasing for different disorder POF are researched, which will open a window to designing a polarization-maintaining random fiber laser.

High-Field-Effect Mobility of Low-Crystallinity Conjugated Polymers with Localized Aggregates.

Charge carriers typically move faster in crystalline regions than in amorphous regions in conjugated polymers because polymer chains adopt a regular arrangement resulting in a high degree of π-π stacking in crystalline regions. In contrast, the random polymer chain orientation in amorphous regions hinders connectivity between conjugated backbones; thus, it hinders charge carrier delocalization. Various studies have attempted to enhance charge carrier transport by increasing crystallinity. However, these approaches are inevitably limited by the semicrystalline nature of conjugated polymers. Moreover, high-crystallinity conjugated polymers have proven inadequate for soft electronics applications because of their poor mechanical resilience. Increasing the polymer chain connectivity by forming localized aggregates via π-orbital overlap among several conjugated backbones in amorphous regions provides a more effective approach to efficient charge carrier transport. A simple strategy relying on the density of random copolymer alkyl side chains was developed to generate these localized aggregates. In this strategy, steric hindrance caused by these side chains was modulated to change their density. Interestingly, a random polymer exhibiting low alkyl side chain density and crystallinity displayed greatly enhanced field-effect mobility (1.37 cm(2)/(V·s)) compared with highly crystalline poly(3-hexylthiophene).

Sulfonated poly(meta‐phenylene isophthalamide)s as proton exchange membranes

ABSTRACTRandom and block sulfonated poly(meta‐phenylene isopthalamide)s as proton exchange membranes were synthesized through the Higashi‐Yamazaki phosphorylation method. Polymers with different degrees of sulfonation from 40 to 100 mol percent were prepared by adjusting the molar feed ratio of 5‐sulfoisophthalic acid sodium salt (SIPA) and isophthalic acid (IPA) in the reaction with meta‐phenylene diamine. Creasable polymer films were obtained by casting DMSO polymer solutions and the membrane films could be exchanged to the proton form in strong acid. 1H NMR spectroscopy and titration confirmed the degree of sulfonation. Thermogravimetric analysis demonstrated good thermal stabilities with 5% weight loss greater than 380 °C. The copolymers with low degrees of sulfonation (DS = 40 mol %) exhibited low water uptake (water uptake &lt; 17 wt %) at room temperature. A segmented multiblock copolymer prepared by preforming a sulfonated block showed lower water uptake at high temperatures than the random polymer with the same DS of 40 mol % and displayed stability in water up to 80 °C. Both random and block copolymers showed higher proton conductivities at high temperature than that of Nafion‐117 under 95% relative humidity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2582–2592