Planar multilayer assemblies containing block copolymer aggregates

Steric Effects in the Deposition Mode and Drug-Delivering Efficiency of Nanocapsule-Based Multilayer Films

Using surface-initiated atom transfer radical polymerization (ATRP), block polymers with a series of quaternization degrees were coated on the surface of silica nanocapsules (SNCs) by the "grafting-from" technique. Molnupiravir, an antiviral medicine urgently approved for the treatment of SARS-CoV-2, was encapsulated in polymer-coated SNCs and further incorporated into well-defined films with polystyrene sulfonate (PSS) homopolymers by layer-by-layer (LBL) self-assembly via electrostatic interactions. We investigated the impact of the quaternization degree of the polymers and steric hindrance of functional groups on the growth mode, swelling/deswelling transition, and drug-delivering efficiency of the obtained LBL films. The SNCs were derived from coronas of parent block polymers of matched molecular weights-poly(N-isopropylacrylamide)-block-poly(N,N-dimethylaminoethyl methacrylate) (PNIPAM-b-PDMAEMA)-by quaternization with methyl sulfate. As revealed by the data results, SNCs with coronas with higher quaternization degrees resulted in a larger layering distance of the film structure because of weaker ionic pairing (due to the presence of a bulky methyl spacer) between SNCs and PSS. Interestingly, when comparing the drug release profile of the encapsulated drugs from SNC-based films, the release rate was slower in the case of capsule coronas with higher quaternization degrees because of the larger diffusion distance of the encapsulated drugs and stronger hydrophobic-hydrophobic interactions between SNCs and drug molecules.

Polyelectrolyte multilayer-like films from layer-by-layer processing of protected polyampholytic block copolymers

Polyelectrolyte multilayer films (PEMs) are conventionally prepared by a layer-by-layer (LbL) deposition of alternating polycation and polyanion solutions. We introduce herein a block copolymer (BCP) approach employing a BCP with an H-bond acceptor block and a protected H-donor block as a masked polyampholyte to form new types of PEMs.

Spherical blackberry-type capsules containing block copolymer aggregates

The design, preparation, and properties of nanosized blackberry-like structures are described. These capsules are composed of two layers of individual block copolymer aggregates, relatively large core vesicles onto which is deposited a layer of smaller vesicles or micelles. The composition of the adjacent layers is such as to ensure strong electrostatic interactions between them. The core vesicles are typically composed of either PS-b-P4VP with a positively charged corona or of PS-b-PAA with a negatively charged corona, and are surrounded by a layer of smaller, oppositely charged block copolymer vesicles or micelles. These composite structures bear a strong resemblance to blackberries, hence the proposed name. The blackberry structures can be prepared in solution or on a flat surface, for example, a silicon wafer. Four compositional possibilities for the blackberries structures were studied, in which the positively or negatively charged core vesicles are covered either by a layer of oppositely charged micelles or by vesicles. These structures represent the earliest stage of a layer-by-layer approach of small spherical aggregates onto a larger spherical hollow core. The strong interaction between the contacting layers is achieved by electrostatic interactions or by complementary acid-base properties, for example, H-bonding. These multicompartmented capsules could be used potentially as delivery vehicles for multiple components; each layer of the capsules could be loaded with hydrophobic (in the core of the micelles or vesicle wall) or hydrophilic molecules (in the vesicle cavity). The overall size of such structures can vary, but in any case can be kept below 1 μm.