Block length-dependent phase transition of poly(N-isopropylacrylamide)-b-poly(2-isopropyl-2-oxazoline) diblock copolymer in water

In Situ Growth of Multiresponsive Structural Color Patterns within Hydrogels for Multiple Information Encryption

Mimicking natural organisms to directly fabricate multiresponsive structural color patterns from small molecules is of great significance for information encryption but remains challenging. Herein, we present a bionic entanglement-interlocking microphase separation strategy for in situ growth of multiresponsive structural color patterns within hydrogel matrixes. The precursor solutions of common polymerization-induced phase-separated materials are used as small-molecule nutrients. The newly generated polymer networks can thus spontaneously collapse into phase-separated microspheres within hydrogels during polymerization. In particular, the dense internetwork entanglements form between the microspheres and hydrogel networks during phase separation, anchoring the microspheres firmly onto hydrogel networks to hinder their gathering. Consequently, these newly grown microspheres can be maintained at the desired nanoscale for yielding the structural blue color by light scattering. Multiresponsive schemochrome patterns can be readily created by growing different microspheres within hydrogel matrixes for multiple information encryptions. We demonstrate that this facile self-growth strategy is applicable to different polymerization-induced phase-separated materials and hydrogel matrixes, regardless of cross-linking modes and geometries.

Synthesis and characterization of a pH/temperature-dual responsive hydrogel with promising biocompatibility features for stimuli-responsive 5-FU delivery

The tunable properties of stimuli-responsive copolymers or hydrogels enable their application in different fields such as biomedical engineering, tissue engineering, or even drug release. Here we introduce a new PNIPAM-based triblock copolymer material comprising a controlled amount of a novel hydrophobic crosslinker 2,4'-diacryloyloxy benzophenone (DABP) and acrylic acid (AAc) to achieve lower critical solution temperature (LCST) between ambient and body temperatures. The dual stimuli-responsive p(NIPAM-co-DABP-co-AAc) triblock copolymer material and hydrogel were synthesized, and their temperature and pH-responsive behaviors were systematically investigated. The hydrogel exhibited excellent temperature and pH-responsive properties with an LCST of around 30 °C. Moreover, the synthesized copolymer has been demonstrated to be nontoxic both in vitro and in vivo. When the hydrogel was preloaded with the model drug 5-fluorouracil (5-FU), the designed hydrogel released the drug in a temperature and pH-controlled fashion. It was observed that the prepared hydrogel has the ability to entrap 5-FU, and the loading is more than 85%. In the case of temperature-controlled release, we observed almost complete release of 5-FU at lower temperatures and sustained release behavior at higher temperatures. In addition, the hydrogel matrix was able to retard the release of 5-FU in an acidic environment and selectively release 5-FU in a basic environment. By realizing how the hydrogel properties influence the release of drugs from preloaded hydrogels, it is possible to design new materials with myriad applications in the drug delivery field.

Block copolymers comprising degradable poly(2-ethyl-2-oxazoline) analogues via copper-free click chemistry

We present the synthesis development of amphiphilic, degradable poly(2-ethyl-2-oxazoline) (PEtOx) analogue block copolymers in a modular fashion utilizing the strain-promoted azide–alkyne cycloaddition (SPAAC).

Poly(2-isopropyl-2-oxazoline)-b-poly(lactide) (PiPOx-b-PLA) Nanoparticles in Water: Interblock van der Waals Attraction Opposes Amphiphilic Phase Separation

Poly(2-isopropyl-2-oxazoline)-b-poly(lactide) (PiPOx-b-PLA) diblock copolymers comprise two miscible blocks: the hydrophilic and thermosensitive PiPOx and the hydrophobic PLA, a biocompatible and biodegradable polyester. They self-assemble in water, forming stable dispersions of nanoparticles with hydrodynamic radii (R h) ranging from ∼18 to 60 nm, depending on their molar mass, the relative size of the two blocks, and the configuration of the lactide unit. Evidence from 1H nuclear magnetic resonance spectroscopy, light scattering, small-angle neutron scattering, and cryo-transmission electron microscopy indicates that the nanoparticles do not adopt the typical core-shell morphology. Aqueous nanoparticle dispersions heated from 20 to 80 °C were monitored by turbidimetry and microcalorimetry. Nanoparticles of copolymers containing a poly(dl-lactide) block coagulated irreversibly upon heating to 50 °C, forming particles of various shapes (R h ∼ 200-500 nm). Dispersions of PiPOx-b-poly(l-lactide) coagulated to a lesser extent or remained stable upon heating. From the entire experimental evidence, we conclude that PiPOx-b-PLA nanoparticles consist of a core of PLA/PiPOx chains associated via dipole-dipole interactions of the PLA and PiPOx carbonyl groups. The core is surrounded by tethered PiPOx loops and tails responsible for the colloidal stability of the nanoparticles in water. While the core of all nanoparticles studied contains associated PiPOx and PLA blocks, fine details of the nanoparticles morphology vary predictably with the size and composition of the copolymers, yielding particles of distinctive thermosensitivity in aqueous dispersions.