Aggregation Behavior of Poly(ethylene glycol-bl-propylene sulfide) Di- and Triblock Copolymers in Aqueous Solution

Abstract

Block copolymers of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS) have recently emerged as a new macromolecular amphiphile capable of forming a wide range of morphologies when dispersed in water. To understand better the relationship between stability and morphology in terms of the relative and absolute block compositions, we have synthesized a collection of PEG-PPS block copolymers and quantified their critical aggregation concentration and observed their morphology using cryogenic transmission electron microscopy after thin film hydration with extrusion and after solvent dispersion from tetrahydrofuran, a solvent for both blocks. By understanding the relationship between aggregate character and block copolymer architecture, we have observed that whereas the relative block lengths control morphology, the stability of the aggregates upon dilution is determined by the absolute block length of the hydrophobic PPS block. We have compared results obtained with PEG-PPS to those obtained with poly(ethylene glycol)-bl-poly(propylene oxide)-bl-poly(ethylene glycol) block copolymers (Pluronics). The results reveal that the PEG-PPS aggregates are substantially more stable than Pluronic aggregates, by more than an order of magnitude. PEG-PPS can form a wide variety of stable or metastable morphologies in dilute solution within normal time and temperature ranges, whereas Pluronics can generally form only spherical micelles under the same conditions. On the basis of these results, block copolymers of PEG with poly(propylene sulfide) may present distinct advantages over those with poly(propylene glycol) for a number of applications.

Immunotheranostic Polymersomes Modularly Assembled from Tetrablock and Diblock Copolymers with Oxidation-Responsive Fluorescence

“…N -(3-bromopropyl)phthalimide end-capped PEG-PPS block copolymers (PEG-PPS-PI) were synthesized by anionic ring opening polymerization of propylene sulfide, initiated by PEG thioacetate and terminated by addition of N -(3-bromopropyl)phthalimide, as previously described. 24 The removal of the phthaloyl group from PEG-PPS-PI to form amino end-functionalized PEG-PPS block copolymer (PEG-PPS-NH 2 ) was accomplished following a previously described method. 24 Polymer-bound isothiocyanate (PITC, 100-200 mesh, extent of labeling: 1.0-2.0 mmol/g loading, 1% crosslinked with divinylbenzene) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) were purchased from Aldrich.…”

“…24 The removal of the phthaloyl group from PEG-PPS-PI to form amino end-functionalized PEG-PPS block copolymer (PEG-PPS-NH 2 ) was accomplished following a previously described method. 24 Polymer-bound isothiocyanate (PITC, 100-200 mesh, extent of labeling: 1.0-2.0 mmol/g loading, 1% crosslinked with divinylbenzene) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) were purchased from Aldrich.…”

“…19-22 The hydrophobic PPS block initiates the self-assembly and is responsible for aggregate stability, providing a critical micelle concentration bellow 10 -7 M. 23 Depending on the individual block lengths, these copolymers can be engineered into a variety of different nanostructures, including solid-core spherical micelles (PEG 44 - bl -PPS 29 , MCs), vesicular polymersomes (PEG 17 - bl -PPS 30 , PSs), and cylindrical filomicelles (PEG 45 - bl -PPS 44 , FMs). 19, 20, 24-26 Each nanostructure achieves a distinct biodistribution and accommodates the loading of small molecules, biologics, fluorophores and contrast agents for multimodality imaging. 20, 25, 27 The polymersome morphology is particularly versatile in that both hydrophobic and hydrophilic payloads can be retained within its lipophilic membrane and aqueous lumen, respectively, for diverse theranostic and imaging strategies.…”

Nanotechnology Advances in Drug Delivery

“…(ii) They can self-assemble into nanostructures at very low critical aggregation concentration (CAC) [35]. A very low Scheme 1: Generic chemical structure of A) poly(ethylene glycol) -poly(propylene sulfide) (PEG-PPS) diblock copolymers [32]; B) poly(ethylene glycol) -poly(propylene sulfide) -(polyethylene imine) (PEG-PPS-ss-PEI) triblock copolymers [39]; C) poly(ethylene glycol) -oligo(ethylene sulfide) (PEG-OES) diblock copolymer [40]; D-F) schematic representation of a micelle, a vesicle and a nanofiber respectively.…”

Engineering Nanomaterials to Address Cell-Mediated Inflammation in Atherosclerosis

“…Immunotherapies have primarily focused on manipulating APCs with an emphasis on DCs, which have been shown to influence the maturation and homeostasis of atheromas [41–43]. Furthermore, DCs have evolved to interact with viruses and can thus be targeted and manipulated by nanomaterials that mimic viral structures and functions [134–137]. Notably, the specific functions of DCs depend on their subset, as some are proatherogenic [43] and others atheroprotective [42].…”