Temperature and concentration effects on supramolecular aggregation and phase behavior for poly(propylene oxide)–b-poly(ethylene oxide)–b-poly(propylene oxide) copolymers of different concentration in aqueous mixtures, 2

Micellar assembly leading to structural growth/transition in normal and reverse Tetronics® in single and mixed solution environment

This study scrutinizes the self-association of ethylene oxide (EO)-propylene oxide (PO)-based star-shaped block copolymers as normal Tetronic® (T904) and reverse Tetronic® R (T90R4) with varying molecular characteristics and different hydrophilic-hydrophobic ratios in an aqueous solution environment. These thermo-responsive solutions appear clear, transparent or bluish up to 10%w/v, which anticipated the probable transition of unimers to spherical or ellipsoidal micelles which is complemented by scattering experiments. In a single-solution environment, 10%w/v T904 formed star-shaped micelles at ambient temperature and exhibited a micellar growth/transition with temperature ageing. While 10%w/v T90R4 exists as unimers or a Gaussian coil over a wide range of temperature. Very interestingly, close to the cloud point (CP) flower-shaped spherical and ellipsoidal micelles were formed. A similar proposed micellar scheme was also examined for mixed systems T904 : T90R4 in varying ratios (1 : 0, 3 : 1, 1 : 1, 1 : 3 and 0 : 1) giving an account to the solution behavior of the mixtures. An amalgamation of dynamic light scattering (DLS) and small-angle neutron scattering (SANS) techniques achieved the thorough extraction of the structural parameters of the micellar system. The hydrodynamic diameter (D_h) of the micelles with temperature variation was evaluated from dynamic light scattering (DLS) while the structure factor of the micelles was found by employing small-angle neutron scattering (SANS). Furthermore, the single and mixed micellar systems were quantitatively and qualitatively examined for anticancer drug solubilization using UV-vis spectroscopy for their superior use as potential nanocargos.

Impact of small molecule and reverse poloxamer addition on the micellization and gelation mechanisms of poloxamer hydrogels

Poloxamer 407 (P407) is widely used for targeted drug-delivery because it exhibits thermoresponsive gelation behavior near body temperature, stemming from a disorder-to-order transition. Hydrophobic small molecules can be encapsulated within P407; however, these additives often negatively impact the rheological properties and lower the gelation temperatures of the hydrogels, limiting their clinical utility. Here we investigate the impact of adding two BAB reverse poloxamers (RPs), 25R4 and 31R1, on the thermal transitions, rheological properties, and assembled structures of P407 both with and without incorporated small molecules. By employing a combination of differential scanning calorimetry (DSC), rheology, and small-angle x-ray scattering (SAXS), we determine distinct mechanisms for RP incorporation. While 25R4 addition promotes inter-micelle bridge formation, the highly hydrophobic 31R1 co-micellizes with P407. Small molecule addition lowers thermal transition temperatures and increases the micelle size, while RP addition mitigates the decreases in modulus traditionally associated with small molecule incorporation. This fundamental understanding yields new strategies for tuning the mechanical and structural properties of the hydrogels, enabling design of drug-loaded formulations with ideal thermal transitions for a range of clinical applications.

Rational Design of Sustainable Liquid Microcapsules for Spontaneous Fragrance Encapsulation

The high volatility, water-immiscibility, and light/oxygen-sensitivity of most aroma compounds represent a challenge to their incorporation in liquid consumer products. Current encapsulation methods entail the use of petroleum-based materials, initiators, and crosslinkers as well as mixing, heating, and purification steps. Hence, more efficient and eco-friendly approaches to encapsulation must be sought. Herein, we propose a simple method by making use of a pre-formed amphiphilic polymer and employing the Hansen Solubility Parameters approach to determine which fragrances could be encapsulated by spontaneous coacervation in water. The coacervates do not precipitate as solids but they remain suspended as colloidally stable liquid microcapsules, as demonstrated by fluorescence correlation spectroscopy. The effective encapsulation of fragrance is proven through confocal Raman spectroscopy, while the structure of the capsules is investigated by means of cryo FIB/SEM, confocal laser scanning microscopy, and small-angle X-ray scattering.

Gels with sense: supramolecular materials that respond to heat, light and sound

Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are "smart" gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal-organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo- and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.

Microparticle templating as a route to nanoscale polymer vesicles with controlled size distribution for anticancer drug delivery

Polymer vesicles are self-assembled shells of amphiphilic block copolymers (BCPs) that have attracted tremendous interest due to their encapsulation ability and intracellular delivery of therapeutic agents. However, typical processes for the formation of polymer vesicles lead to ensembles of structures with a broad size distribution (from nanometer to micrometer scale) which result in a limitation for efficient cellular uptake. In this study, we present a simple and efficient approach for the fabrication of polymer vesicles with uniform nanoscale dimensions from template formation of electrosprayed particles in a high throughput manner. First, electrospraying was applied to produce micrometer-sized templates of a block copolymer before polymer vesicles were formed from the pre-prepared microparticles via rehydration. Four different biocompatible diblock and triblock copolymers were used to successfully fabricate polymer vesicles with uniform size around 150nm using this approach. Furthermore, we encapsulate anticancer drug doxorubicin (DOX) within the polymer vesicles via this method. The kinetics of cellular uptake (HeLa cell) and intracellular distribution of DOX-loaded polymer vesicles have been quntified and monitored by flow cytometry and confocal microscopy, respectively. The results show that our new method provides a promising way to fabricate drug-loaded polymer vesicles with controllable nanoscale size for intracellular anticancer drug delivery.

Nanoparticle Vesicles with Controllable Surface Topographies through Block Copolymer-Mediated Self-Assembly of Silica Nanospheres

Silica nanoparticle vesicles (NPVs) with encapsulating capability and surface permeability are highly attractive in nanocatalysis, biosensing, and drug delivery systems. Herein, we report the facile fabrication of silica NPVs composed of a monolayer of silica nanospheres (SNSs, ca. 15 nm in diameter) through the block copolymer-mediated self-assembly of SNSs. The silica NPVs gain different surface topographies, such as raspberry- and brain coral-like topographies, under controlled heat treatment conditions. The vesicular assembly of SNSs is successful with a series of poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) block copolymers, and the size of NPVs can be tuned by changing their molecular weight. The polymer is easily extracted from the NPVs with their colloidal dispersibility and structural integrity intact. The polymer-free silica NPVs further serve as a reaction vessel and host for functional materials such as tin oxide nanoparticles.

Premicellar interaction of PEO-PPO-PEO triblock copolymers with partially hydrophobic alcohols: NMR study

The interactions of three alcohols, namely, 2-butanol (BuOH), 3-methyl-2-butanol (MeBuOH), and 3,3-dimethyl-2-butanol (Me2BuOH) with propylene oxide octamer (PO8) and the copolymers (EO)8(PO)13(EO)8(L35) and (EO)13(PO)30(EO)13(L64) in D2O were studied using (13)C NMR spectra and relaxations and (1)H PFG NMR diffusion measurements. For L64, it was shown that the temperature at which the PO chain starts to change its conformation under dehydration decreases by 6 K for each additional methyl group in the alcohol molecule (i.e. with increasing its hydrophobicity), and the analogous conformation states are attained at temperatures approximately 10 K lower compared using ketonic analogs of the alcohols under the same conditions. Also, the first signs of L64 aggregation, according to the normalized diffusion coefficients, are at temperatures 7, 10, and 13 K lower for BuOH, MeBuOH, and Me2BuOH, respectively. These effects are much weaker for (PO)13 in L35 or nonexistent for (PO)8 in PO8, thus showing the role of cooperativity in dehydration and aggregation processes. According to diffusion measurements, the molar fraction of the alcohol hydrogen bonded to L64 increases with its hydrophobicity and, in an apparent conflict with thermodynamics, with increasing temperature at which also higher NOE can be observed. Strong hydrogen bond interaction, which is in cooperation with hydrophobic interaction, does not preclude the exchange between bound and free states of the alcohol, however. Using (13)C transverse relaxation, its correlation time is shown to be of the order of 10 ms.