Block Copolymer Capsules with Structure‐Dependent Release Behavior

Abstract

Although high-boiling non-solvent induced macrophase separation in emulsion droplets has been widely applied for the fabrication of polymeric capsules,p recise control of their structures remains ag reat challenge.H erein, block copolymer capsules with tunable shell structures were fabricated by employing an on-solvent as al iquid template in emulsion droplets.T he properties of the non-solvents dictate the phase separation sequence in the droplets and the capsule formation mechanism. Tw od ifferent pathwaysf or capsule formation were observed, and could be applied to predict the shell structure.T he structured capsules could be transformed into mesoporous capsules,w hichd emonstrated an intriguing structure-dependent release behavior.C apsules with spherical shell structures displayed the best permeability,w hile those with lamellar shell structures showed the slowest release,b ut with astepwise profile.After loading with an anticancer drug, different capsules induced different apoptosis ratios in cancer cell studies.Polymeric capsules are of great importance to many applications,e specially for protecting loaded cargoes against ah arsh environment and releasing them upon exposure to external triggers. [1][2][3][4] Many approaches, [5][6][7] such as phase separation in emulsion droplets, [8][9][10] sacrificial template guided polymerization, [11,12] layer-by-layer assembly techniques, [13][14][15] self-assembly of block copolymers (BCPs) in selective solvents, [16][17][18][19][20] and others,h ave been introduced for preparing polymeric capsules.A mong these methods,t he macrophase separation of ahigh-boiling non-solvent (HBNS, e.g.,l ong-chain alkanes) in emulsion droplets containing al ow-boiling good solvent (LBGS,e .g., chloroform) and ahomopolymer has been developed as asimple yet versatile strategy for obtaining homopolymer capsules. [21][22][23] However, for BCP capsules,the capsule formation process is much more complicated as microphase separation (between blocks) and macrophase separation (between HBNS and BCPs) occur simultaneously in the droplets.C respy and co-workers recently reported the fabrication of BCP patchy capsules using hexadecane (HD) as the liquid cores. [24][25][26] However,the effect of polymer-solvent interactions on the capsule shell structure needs further exploration. Nowadays,i ti ss till agreat challenge to generate BCP capsules with tunable shell structures in ac ontrolled fashion.Although BCP capsules are robust enough for cargo loading and release,t hey are semipermeable and only allow for very small molecules to be loaded and released owing to the hydrophobic shell. To overcome this disadvantage, capsules with stimuli-responsive shells have been designed as smart nanocarriers to encapsulate functional species and release them in response to external triggers. [27][28][29][30] Furthermore,t ot une the release behavior, [20,[31][32][33][34] capsules with stimuli-responsive mesoporous shells are excellent candidates for controlling the release of payloads. [35][36][37][38] Remar...

Advanced functional polymer materials

“…For example, hollow microcapsules with tunable shell structures have been fabricated under confinement, and the release behavior of encapsulated cargoes in these structured capsules was found to be strongly dependent on the shell structure. 528 The above results indicate that confined assembly is a facile yet robust approach to control the shape and internal structure of BCP colloidal particles. Yet, despite the significant progress achieved in recent years, the assembly of BCPs in 3D confined space is still an emerging field.…”

“…When the self-assembly of BCPs takes place within confined spaces, the interfacial interactions, symmetry breaking, structural frustration, and confinement-induced entropy loss of the polymer chains play a dominant role in the final self-assembled structure, thereby resulting in some novel nanostructures that are not available in bulk and solution states. [524][525][526][527][528] Moreover, functional inorganic NPs are usually introduced to coassemble with BCPs or directly assembled with polymer-tethered NPs, which can effectively combine the respective functions of the polymers and NPs. 529,530 Despite the rapidly increasing number of publications related to the self-assembly Under 3D confinement.…”

“…71) have been prepared via confined self-assembly in emulsion droplets, which exhibited angle-independent structural color after swelling in an ethanol/water mixed solution. 528 Interestingly, the structural color can be effectively tuned by varying the ethanol concentration because of the selective swelling of P2VP domains. These photonic microspheres showed potential applications in bio-diagnosis, colorimetric sensors, encoding, and active displays.…”

Mesoscale Simulations of Polymer Solution Self-Assembly: Selection of Model Parameters within an Implicit Solvent Approximation

“…These novel self-assembled microparticles have potential applications, such as drug delivery, photonic devices, etc. [ 66 , 67 ]. However, compared to its potential and amount of experimental efforts, numerical studies are very limited.…”

Controllable Fragrance Release Mediated by Spontaneous Hydrogen Bonding with POSS–Thiourea Derivatives

“…[8][9][10][11][12][13] For instance, the fragrance molecules are enclosed in polymeric materials that can release the fragrances upon the breakage or diffusion of shells. [14][15][16][17][18][19][20][21][22][23][24][25][26] In contrast to physical encapsulation, chemical approaches of profragrances have been developed by Herrmann and others, with chemically covalent binding of volatile molecules to the proper substrates duringthe formation ofprofragrance non-volatiles, 1,[27][28][29][30][31][32][33] wherein the volatile perfume molecules are chemically released with cleavage of a covalent bond or a weak interaction such as hydrogen bond.…”