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The self‐assembly behavior, in aqueous solution, of amphiphilic methacrylic random copolymers with perfluoroalkyl and polyoxyethylene side chains and the morphology of the resulting nanostructures are investigated by small‐angle neutron scattering (SANS). The results allow to clarify the effect of temperature on the self‐assembly features of copolymers and the structural morphology of both unimer single‐chain entities and larger multi‐chain aggregates of unimers. Shape, flexibility, and size of the aggregates are proved to be modulated by temperature and copolymer composition. The existence of three distinct phases of self‐assembled structures is pointed out as a function of increasing temperature: 1) globular unimers; 2) coexistence of extended unimers and aggregates; and 3) aggregates, which overall show full reversibility in a wide range of copolymer concentrations. [ABSTRACT FROM AUTHOR]

Abstract An amphiphilic random copolymer of hydrophilic poly(ethylene glycol) methyl ether methacrylate with hydrophobic perfluorohexylethyl acrylate, PEGMA77 -co- FA23, was synthesized by ATRP and used to investigate self-assembling into nanostructures in water and chloroform solutions, both experimentally and computationally. The dynamic light scattering measurements on water solutions of the copolymer at room temperature evidenced the presence of nanoassemblies with hydrodynamic diameter D h = 4 ± 1 nm. The behavior of fluorescence emission intensity of water solutions with added ethidium bromide suggested confinement of the molecular rotor within a hydrophobic environment of the copolymer. Moreover, these nanoassemblies were thermoresponsive and reversibly collapsed into much larger, multi-chain aggregates with D h = 390 ± 20 nm at a critical temperature of 55 °C (5 mg mL−1). Molecular dynamics simulations revealed the formation of single-chain, prolate globular nanoassemblies with a structural variability in water solution at room temperature. The evolutions of the simulated radius of gyration (R g), asphericity, prolateness and solvent-accessible surface area were analyzed along the folding trajectories. Thus, self-folding appeared to result from the interplay between hydrophobic interactions and structural constraints which leads to rather complex nanostructures (R g = 20–25 Å, 200 ns simulation). By contrast, folding in much more open polymer conformations (R g = 30–40 Å) was predicted for chloroform solutions. Graphical abstract An amphiphilic random copolymer single-chain folds into nanoassemblies in water that appear as prolate globular nanostructures by molecular dynamics simulations. Image 1 Highlights • An ATRP-synthesized, amphiphilic random copolymer self-assembled in water solutions. • Single-chain folded, i.e. unimer, nanoassemblies in water solutions were measured by DLS. • Molecular dynamics simulations evidenced the trajectories of chain folding into compact and prolate nanoassemblies. • Radius of gyration, asphericity, prolateness and solvent-accessible surface area were simulated along the trajectories. [ABSTRACT FROM AUTHOR]

Abstract: Two amphiphilic random copolymers, PEGMAx‐co‐FAy (x = 90 and 70 mol%), are synthesized by ATRP and their solutions are investigated as a function of solvent, concentration, and temperature by DLS and SANS analyses. Both copolymers self‐assemble in nanostructures by single‐chain folding in water solutions over a wide range of temperatures. The values of the DLS hydrodynamic radius and the SANS radius of gyration are found to be ≈4 nm and ≈3.4–3.7 nm, respectively. Moreover, SANS shows the self‐folded nanoassemblies to be prolated spheroids with a ratio of polar/equatorial axes of ≈5:1 for PEGMA90‐co‐FA10 and ≈2:1 for PEGMA70‐co‐FA30. On heating above a critical temperature Tc, multichain microassemblies are formed that revert back to nanoassemblies on cooling below Tc. This temperature‐responsive transition is fully and sharply reversible. [ABSTRACT FROM AUTHOR]

Abstract: Novel amphiphilic random copolymers carrying poly(oxyethylene) and poly(siloxane) pendant chains are synthesized by atom transfer radical polymerization starting from either a fluorescent, julolidine‐based initiator, or a nonfluorescent initiator. For both copolymer systems, dynamic light scattering measurements carried out on aqueous solutions as a function of temperature reveal the occurrence of a sharp and fully reversible transition between two different self‐associative states of individual, single‐chain self‐folded nanoassemblies, so‐called unimer micelles, (Dh = 8–10 nm) and collapsed multichain aggregates (Dh = 700–1400 nm) at a critical temperature Tc. Covalently linked julolidine terminal and added ethidium bromide are separately used as fluorescent probes and both prove the temperature‐dependence of the different self‐association of the copolymers in water. [ABSTRACT FROM AUTHOR]

Water-soluble amphiphilic random copolymers composed of tri(ethylene glycol) methacrylate (TEGMA) or poly(ethylene glycol) methyl ether methacrylate (PEGMA) and perfluorohexylethyl acrylate (FA) were synthesized by ARGET-ATRP, and their self-assembling and thermoresponsive behavior in water was studied by dynamic light scattering (DLS) and UV-vis spectroscopy. The copolymer ability to self-fold in single-chain nano-sized structures (unimer micelles) in aqueous solutions was exploited to encapsulate Combretastatin A-4 (CA-4), which is a very hydrophobic anticancer drug. The cloud point temperature (Tcp) was found to linearly decrease with increasing drug concentration in the drug/copolymer system. Moreover, while CA-4 was preferentially incorporated into the unimer micelles of TEGMA-ran-FA, the drug was found to induce multi-chain, submicro-sized aggregation of PEGMA-ran-FA. Anyway, the encapsulation efficiency was very high (≥81%) for both copolymers. The drug release was evaluated in PBS aqueous solutions both below and above Tcp for TEGMA-ran-FA copolymer and below Tcp, but at two different drug loadings, for PEGMA-ran-FA copolymer. In any case, the release kinetics presented similar profiles, characterized by linear trends up to ≈10–13 h and ≈7 h for TEGMA-ran-FA and PEGMA-ran-FA, respectively. Then, the release rate decreased, reaching a plateau. The release from TEGMA-ran-FA was moderately faster above Tcp than below Tcp, suggesting that copolymer thermoresponsiveness increased the release rate, which occurred anyway by diffusion below Tcp. Cytotoxicity tests were carried out on copolymer solutions in a wide concentration range (5–60 mg/mL) at 37 °C by using Balb/3T3 clone A31 cells. Interestingly, it was found that the concentration-dependent micro-sized aggregation of the amphiphilic random copolymers above Tcp caused a sort of "cellular asphyxiation" with a loss of cell viability clearly visible for TEGMA-ran-FA solutions (Tcp below 37 °C) with higher copolymer concentrations. On the other hand, cells in contact with the analogous PEGMA-ran-FA (Tcp above 37 °C) presented a very good viability (≥75%) with respect to the control at any given concentration. [ABSTRACT FROM AUTHOR]

Amphiphilic hydrolyzable block copolymers composed of a poly(dimethylsiloxane) (PDMS) first block and a random poly(ethyleneglycol methacrylate (PEGMA)- co -trialkylsilyl methacrylate (TRSiMA, R = butyl, isopropyl) second block were synthesized by RAFT polymerization and dispersed as surface-active amphiphilic additives in a condensation cure PDMS matrix. Poly(tributylsilyl methacrylate) (pTBSiMA) and poly(triisopropylsilyl methacrylate) (pTiPSiMA) homopolymers and random copolymers PEGMA- co -TRSiMA were also synthesized as model polymers for comparison. The hydrolysis rates of the polymers in both ammonia buffer and artificial seawater were shown to drastically depend on the nature of the trialkylsilyl groups, with TiPSiMA polymers undergoing a slower rate hydrolysis. The incorporation of PEGMA units in the copolymers was found to increase the hydrolysis rate. On the other hand, the presence of the PDMS block led to a decrease in the hydrolysis rate for the block copolymers. Wettability studies of the elastomer PDMS-based films containing a surface-active additive block copolymer were carried out in both static and dynamic conditions. All the films were found to be both hydrophobic and lipophobic and became more hydrophilic after 30 days of water immersion. Measurements of advancing and receding contact angles with water confirmed the ability of the film surfaces to respond to the water environment. Image 1 • Synthesis of new PDMS-based block copolymers with PEG and trialkylsilyl side groups. • Incorporation of block copolymers in PDMS matrix as amphiphilic hydrolyzable additives. • Hydrolysis rate affected by copolymer composition and trialkylsilyl group chemistry. • Dynamic surface modification in water as a result of hydrolysis and surface migration. [ABSTRACT FROM AUTHOR]

A set of amphiphilic random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and perfluorohexylethyl acrylate (FA) with different compositions synthesized by atom transfer radical polymerization (ATRP) is investigated by 1H and 19F NMR relaxometry. In particular, a thorough investigation of T1 and T2 relaxation times at variable temperature and copolymer composition provides the first complete and detailed characterization of the dynamics of both the main chain backbone and the side chains of the PEGMA‐co‐FA copolymers. The results highlight an intramolecular segregation of rigid main chain and mobile side chains, and an additional self‐assembling of the PEGMA and FA side chains into distinct nanodomains, driven by the hydrophobic interactions between FA side chains. The obtainment and observation of nanoscale phase separation in random copolymers is a promising achievement to the aim of controlling self‐assembly in the bulk by suitably modulating copolymers composition, which can open novel avenues to easier fabrications and applications in nanotechnologies. [ABSTRACT FROM AUTHOR]