Two Polymersome Evolution Pathways in One Polymerization-Induced Self-Assembly (PISA) System

Abstract

Block copolymer polymersomes offer considerable access for applications in a variety of fields; however, the traditional cosolvent self-assembly method can only produce polymersomes at a low solids content (typically <1%). Recently, an in situ growth method, termed polymerization-induced self-assembly (PISA), has been developed to allow the preparation of polymersomes at high solids (10–50%). Synthesis and self-assembly of block copolymers occur simultaneously in PISA, and therefore, morphological evolution occurs throughout the polymerization. It is highly desirable to provide mechanistic insights into morphological evolution that enables one to rationally synthesize a variety of morphologies. Herein, we demonstrate that the further growth of polymersomes in aqueous PISA can be conveniently driven by temperature via two different pathways: (i) at high temperatures from polymersomes with a thin membrane to polymersomes with a thick membrane and (ii) at low temperatures from spherical polymersomes to tubular and donut-like polymersomes. We show that both the hydrodynamic diameter and membrane thickness of polymersomes increase during PISA at high temperatures, indicating that the membrane of polymersomes grows inward and outward simultaneously as the polymerization proceeds. Furthermore, careful characterization of samples withdrawn during the kinetic study at low temperatures by transmission electron microscopy and dynamic light scattering reveals various intermediate morphologies that provide important insights into the formation of tubular and donut-like polymersomes. We expect that this study not only provides mechanistic insights into the morphological evolution of PISA but also expands the scope of PISA for the preparation of a variety of structures.

Shape-shifting thermoreversible diblock copolymer nano-objects via RAFT aqueous dispersion polymerization of 4-hydroxybutyl acrylate

“…TEM analysis of PHPMA-based nano-objects is well established in the literature. 28,34,52,[61][62][63][64][65] Differential scanning calorimetry (DSC) studies indicated a relatively high T g of 94 C aer drying under vacuum for three days at 30 C (Fig. 2a, purple trace) for a PHPMA 200 homopolymer, which is consistent with the literature.…”

Dextran-Coated Latex Nanoparticles via Photo-RAFT Mediated Polymerization Induced Self-Assembly

“…It is well known that the concentration and the size of the hydrophobic block are the keys parameters influencing the morphology of nano-objects in PISA. This has been widely reported in case of PHPMA core forming nano-objects, which can form easily large set of nano-objects morphologies [ 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. However, in case of the present investigation, we observed exclusively spherical micelles.…”

One‐Step Preparation of Thermo‐Responsive Poly(N‐isopropylacrylamide)‐Based Block Copolymer Nanoparticles by Aqueous Photoinitiated Polymerization‐Induced Self‐Assembly

“…This can be attributed to two possible reasons: (i) Higher reaction temperature facilitates the sphere–sphere fusion, a key step for the morphological evolution; (ii) PNIPAM is more hydrophobic and has higher mobility at higher temperature, favoring the micellization as well as the plasticization with NIPAM, which is beneficial for the anisotropic fusion of spherical micelles to form worm‐like and vesicular‐like micelles. [ 40,46,47 ] The morphological evolution can be further controlled by using macro‐RAFT agents with different lengths. For example, higher‐order morphologies could be obtained even at 37 °C when using PDMA 32 –DDMAT as the macro‐RAFT agent (Figure S5, Supporting Information), which can be attributed to the decrease in packing parameter when using a shorter macro‐RAFT agent.…”