Molecular Weight-Independent "Polysoap" Nanostructure Characterized via In Situ Resonant Soft X-ray Scattering

Studying polymer micelle structure and loading dynamics under environmental conditions is critical for nanocarrier applications but challenging due to a lack of in situ nanoprobes. Here, the structure and loading of amphiphilic polyelectrolyte copolymer micelles, formed by 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and n-dodecyl acrylamide (DDAM), were investigated using a multimodal approach centered around in situ resonant soft X-ray scattering (RSoXS). We observe aqueous micelles formed from polymers of wide-ranging molecular weights and aqueous concentrations. Despite no measurable critical micelle concentration (CMC), structural analyses point toward multimeric structures for most molecular weights, with the lowest molecular weight micelles containing mixed coronas and forming loose micelle clusters that enhance hydrocarbon uptake. The sizes of the micelle substructures are independent of both the concentration and molecular weight. Combining these results with a measured molecular weight-invariant surface charge and zeta potential strengthens the link between the nanoparticle size and ionic charge in solution that governs the polysoap micelle structure. Such control would be critical for nanocarrier applications, such as drug delivery and water remediation.

tert-Butylhydroperoxide mediated radical cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s

A novel sustainable methodology based on one-pot cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s involving a three-component radical cascade pathway has been achieved. Here, tert-butylhydroperoxide (TBHP) acts as an efficient oxidant, and it smoothly drives the reaction, producing the three-component products in very good to excellent yields. This cascade reaction eliminates the use of any base, additive, metal and hazardous cyanating agent. Additionally, this protocol exclusively delivers a stereospecific product in the case of arylalkynes. The involvement of radicals is evidenced through various radical trapping experiments.

Synthesis of poly(n-alkyl acrylamides) and evaluation of nanophase separation effects by temperature-dependent infrared spectroscopy

Common linear polymers are known to undergo phase changes at the glass-transition temperature (Tg) and the melting point (Tm). In recent years, it has also been shown that molecules with long aliphatic side chains can give rise to a backbone-independent melting phenomenon, known as nanophase separation. This effect describes the self-assembly — independent of the polymer backbone — of alkyl side chains into semi-crystalline nanostructures. This work presents optimized, gram scale synthesis routes for dodecyl and octadecyl acrylamide and their respective homopolymers. Differential scanning calorimetry (DSC) experiments detected a broad endothermal signal for poly(n-dodecyl acrylamide) at − 29 °C and a narrower, more intense signal for poly(n-octadecyl acrylamide) at 34 °C. These signals indicate the nanophase separation TM of the alkyl side chains. We undertook the first temperature-controlled infrared spectroscopy investigations of these materials revealing a clear hypsochromic shift of the C–H stretching signals above TM and the amide I signal shifts that occurred only above and below Tg. These results provide further evidence, that the side chains act independently of the polymer backbone and show that infrared spectroscopy is a powerful tool for monitoring conformational changes in polymer side chains.

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Metal-free three-component cyanoalkylation of quinoxalin-2(1H)-ones with vinylarenes and azobis(alkylcarbonitrile)s

A K2S2O8-mediated C3 cyanoalkylation of quinoxalin-2(1H)-ones via a three-component radical cascade reaction with vinylarenes and azobis(alkylcarbonitrile)s has been achieved.

Using Microemulsion Phase Behavior as a Predictive Model for Lecithin-Tween 80 Marine Oil Dispersant Effectiveness

Marine oil dispersants typically contain blends of surfactants dissolved in solvents. When introduced to the crude oil-seawater interface, dispersants facilitate the breakup of crude oil into droplets that can disperse in the water column. Recently, questions about the environmental persistence and toxicity of commercial dispersants have led to the development of "greener" dispersants consisting solely of food-grade surfactants such as l-α-phosphatidylcholine (lecithin, L) and polyoxyethylenated sorbitan monooleate (Tween 80, T). Individually, neither L nor T is effective at dispersing crude oil, but mixtures of the two (LT blends) work synergistically to ensure effective dispersion. The reasons for this synergy remain unexplained. More broadly, an unresolved challenge is to be able to predict whether a given surfactant (or a blend) can serve as an effective dispersant. Herein, we investigate whether the LT dispersant effectiveness can be correlated with thermodynamic phase behavior in model systems. Specifically, we study ternary "DOW" systems comprising LT dispersant (D) + a model oil (hexadecane, O) + synthetic seawater (W), with the D formulation being systematically varied (across 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 L:T weight ratios). We find that the most effective LT dispersants (60:40 and 80:20 L:T) induce broad Winsor III microemulsion regions in the DOW phase diagrams (Winsor III implies that the microemulsion coexists with aqueous and oil phases). This correlation is generally consistent with expectations from hydrophilic-lipophilic deviation (HLD) calculations, but specific exceptions are seen. This study then outlines a protocol that allows the phase behavior to be observed on short time scales (ca. hours) and provides a set of guidelines to interpret the results. The complementary use of HLD calculations and the outlined fast protocol are expected to be used as a predictive model for effective dispersant blends, providing a tool to guide the efficient formulation of future marine oil dispersants.

Label-free characterization of organic nanocarriers reveals persistent single molecule cores for hydrocarbon sequestration

Self-assembled molecular nanostructures embody an enormous potential for new technologies, therapeutics, and understanding of molecular biofunctions. Their structure and function are dependent on local environments, necessitating in-situ/operando investigations for the biggest leaps in discovery and design. However, the most advanced of such investigations involve laborious labeling methods that can disrupt behavior or are not fast enough to capture stimuli-responsive phenomena. We utilize X-rays resonant with molecular bonds to demonstrate an in-situ nanoprobe that eliminates the need for labels and enables data collection times within seconds. Our analytical spectral model quantifies the structure, molecular composition, and dynamics of a copolymer micelle drug delivery platform using resonant soft X-rays. We additionally apply this technique to a hydrocarbon sequestrating polysoap micelle and discover that the critical organic-capturing domain does not coalesce upon aggregation but retains distinct single-molecule cores. This characteristic promotes its efficiency of hydrocarbon sequestration for applications like oil spill remediation and drug delivery. Such a technique enables operando, chemically sensitive investigations of any aqueous molecular nanostructure, label-free.

Development of aqueous size exclusion chromatography conditions to characterize polyzwitterion-block-N-isopropyl acrylamide copolymers

Block copolymers that exhibit both an upper critical solution temperature and a lower critical solution temperature are difficult to characterize due to inherent solubility difference between the two blocks. For example, accurate determination of both the molar mass and molar mass distribution is challenging for polyzwitterion-block-N-isopropyl acrylamide (NIPAM) copolymers in aqueous solutions due to self-assembly. However, there are a few examples of using size exclusion chromatography (SEC) for characterization, in which hexafluoro isopropanol (HFIP) is used in all cases. Yet, researchers are hesitant to use this solvent due to how expensive and hazardous HFIP is. Therefore, alternatives to HFIP for SEC analysis would be desirable. Here, a systematic methodology featuring aqueous SEC is demonstrated using several solvent conditions to enable the elution of polyzwitterion-block-NIPAM copolymers on Agilent PolarGel^† and Tosoh TSKgel^† column sets. These SEC conditions include 0.2 M KI in water on the PolarGel columns and 0.2 M KI/ 30% DMF in water on the PolarGel and TSKgel columns. These aqueous systems can be utilized for the characterization of similar water-soluble block copolymers that are relevant for drug delivery and other biomedical applications.

Well-controlled polymerization of tri-vinyl dynamic covalent boroxine monomer: one dynamic covalent boroxine moiety toward a tunable penta-responsive polymer

Attributed to dynamic characteristics of dynamic covalent boroxine, well-controlled polymerization of tri-vinyl monomer and molecular design of penta-responsive polymer with only one functional moiety are achieved.

Poly(triazolyl methacrylate) glycopolymers as potential targeted unimolecular nanocarriers

Synthetic glycopolymers are increasingly investigated as multivalent ligands for a range of biological and biomedical applications. This study indicates that glycopolymers with a fine-tuned balance between hydrophilic sugar pendant units and relatively hydrophobic polymer backbones can act as single-chain targeted nanocarriers for low molecular weight hydrophobic molecules. Non-covalent complexes formed from poly(triazolyl methacrylate) glycopolymers and low molecular weight hydrophobic guest molecules were characterised through a range of analytical techniques - DLS, SLS, TDA, fluorescence spectroscopy, surface tension analysis - and molecular dynamics (MD) modelling simulations provided further information on the macromolecular characteristics of these single chain complexes. Finally, we show that these nanocarriers can be utilised to deliver a hydrophobic guest molecule, Nile red, to both soluble and surface-immobilised concanavalin A (Con A) and peanut agglutinin (PNA) model lectins with high specificity, showing the potential of non-covalent complexation with specific glycopolymers in targeted guest-molecule delivery.

Pincushion of Tubule Discovery and Tubular Morphology Landscape Establishment of Block Copolymer Self-Assemblies

Block copolymer (BCP) self-assembly is a versatile technique in the preparation of polymeric aggregates with varieties of morphologies. However, its morphology library is limited. Here, the discovery of pincushion of tubules is reported for the first time, via BCP self-assembly of poly(4-vinylpyridine)-b-polystyrene (P4VP-b-PS) with very high molecular weight (500 kDa) and asymmetry (2 mol% P4VP). The investigation confirms the importance of core-forming block length on morphology control of BCP self-assemblies, especially with respect to tubular structures. The morphology landscape of tubular structures is successfully established, where dumbbell of tubule, tubule, loose clew of tubules, tight clew of tubules, and pincushion of tubules can be prepared by adjusting the core-forming block length. This work therefore expands the structure library of BCP self-assemblies and opens up a new avenue for the further applications of these tubular materials.

Borinic Acid Polymer: Simplified Synthesis and Enzymatic Biofuel Cell Application

A simplified one-pot and less harmful method has been introduced for the synthesis of borinic acid monomer. The corresponding borinic acid polymer (PBA) has been prepared by reversible addition-fragmentation chain transfer polymerization. Property investigations confirm the characteristics of PBA as a new type of "smart material" in the field of thermo-responsive polymer. The potential application of PBA in the field of enzymatic biofuel cell has been illustrated with a wide open circuit potential of 0.92 V.

Amphiphilic acrylamide block copolymer: RAFT block copolymerization and monolayer behaviour

Amphiphilic acrylamide block copolymer, synthesized by RAFT polymerization, takes a stable monolayer formation with phase-separated structures at the air–water interface.

Expanding the morphology library of block copolymer self-assemblies with clews of tubules

Clews of tubules are reported via block copolymer self-assembly of P4VP-b-PS with both high asymmetry and very high molecular weight.

Versatile Method to Expand the Morphology Library of Block Copolymer Solution Self-Assemblies with Tubular Structures

Self-assembly of block copolymers (BCPs) in solution is a powerful technology to achieve a broad range of structures, such as spheres, cylinders, vesicles, and other hierarchical structures. However, the BCP self-assembly library is limited, especially with respect to tubular structures. Here we show a versatile strategy to expand the morphology library of block copolymer solution self-assemblies with tubular structures (including tubular dumbbells and tubules) via self-assembly of the most common diblock copolymers P4VP-b-PS BCPs in methanol. No special chemistry is needed in this strategy, which proves the universality of this method. The novelty of the strategy is to keep the BCPs both highly asymmetric and with very high molecular weight. The underlying formation mechanism and kinetics of these tubular structures were elucidated. The prepared tubular structures expand the structure library of BCP solution self-assemblies and open up a new avenue for the further applications of a variety of tubular materials.

Thermo-responsive rheological behavior of borinic acid polymer in dilute solution

Borinic acid polymer is rheologically thermo-responsive in solution, which expands its application as a new type of “smart” polymer.

Post polymer modification of polyethylenimine with citrate esters: selectivity and hydrophobicity

Hydrophobic modification of water soluble PEI with citrate esters is selective and increases log P_oct.

Investigation of Optimum Polymerization Conditions for Synthesis of Cross-Linked Polyacrylamide-Amphoteric Surfmer Nanocomposites for Polymer Flooding in Sandstone Reservoirs

Currently enhanced oil recovery (EOR) technology is getting more attention by many countries since energy crises are getting worse and frightening. Polymer flooding by hydrophobically associated polyacrylamides (HAPAM) and its modified silica nanocomposite are a widely implemented technique through enhanced oil recovery (EOR) technology. This polymers class can be synthesized by copolymerization of acrylamide (AM), reactive surfmer, functionalized silica nanoparticles, and a hydrophobic cross-linker moiety in the presence of water soluble initiator via heterogeneous emulsion polymerization technique, to form latexes that can be applied during polymer flooding. Chemical structure of the prepared copolymers was proven through different techniques such as Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic spectroscopy (1H&13C-NMR), and molecular weight was measured by gel permeation chromatography. Study of the effects of monomer, surfmer, cross-linker, silica, and initiator concentrations as well as reaction temperature was investigated to determine optimum polymerization conditions through single factor and orthogonal experiments. Evaluation of the prepared copolymers for enhancing recovered oil amount was evaluated by carrying out flooding experiments on one-dimensional sandstone model to determine recovery factor.