Controlling Internal Pore Sizes in Bicontinuous Polymeric Nanospheres

Abstract

Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17 kDa and hydrophilic weight fractions of ≤0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460 nm. Significantly, altering the block copolymer hydrophilic–hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19 nm.

CryoTEM as an Advanced Analytical Tool for Materials Chemists

“…While cryoTEM is becoming a more and more widespread technique for the characterization of a wide variety of biological structures, cryoET is still relatively unexplored for synthetic organic materials, as is exemplified by our study of bicontinuous polymer nanoparticles discussed below. 20,22−24 We also use this example to illustrate the possibility of using cryoTEM to monitor self-assembly in the presence of organic solvents, and eventually show how cryoET can even be used in a fully organic solvent to reveal the 3D structure of P3HT nanowires as well as to monitor the development of crystallinity in the system. 25 …”

Interfacial Crystallization‐Driven Assembly of Conjugated Polymers/Quantum Dots into Coaxial Hybrid Nanowires: Elucidation of Conjugated Polymer Arrangements by Electron Tomography

“…Recently, the direct visualization of nanomaterials through electron tomography (ET) has been used to elucidate the spatial organization of nanostructures [ 34,35 ] that are confounded by overlapped internal features, such as nano/microparticles containing pores and channels [ 36 ] and inorganic nanoparticles embedded in colloidal polymer particles. [ 37 ] The intimate relationship between nanostructure and property has been studied.…”

Controlling the melting transition of semi-crystalline self-assembled block copolymer aggregates: controlling release rates of ibuprofen

“…The self-assembly of BPNs from PEO-b-PODMA has been investigated previously by Holder and Sommerdijk et al and it was found that the weight fraction of the hydrophilic block (PEO) should be between 15-25% with the molecular weight at < 17 kDa for BPNs to form. 7 In this case the hydrophobic PODMA block exhibited a melting transition due to the crystallisation of the long alkyl side chains. It was subsequently established that the Tm of the ODMA block affected the rate of release of a hydrophobic compound into the surrounding aqueous medium; pyrene was encapsulated within the BPNs and above the Tm of the PODMA block (21°C), the rate of release increased significantly.…”

“…A modification of a well reported literature method [6][7][8]27 was used for the synthesis of the PEO49-b-PODMA21 homopolymer via ATRP using a PEO macroinitiator and a Cu(I)Br/PMDETA catalyst (Scheme 1). The same procedure was also followed for the synthesis of the PEO-b-PDSMA homopolymer and the PEOb-(PODMA-co-PDSMA) copolymers.…”

“…This result is consistent with previous observations for the same BCP. [6][7][8]22 The change in H ) values given in Table 2 were calculated from the peak area (J/g) using Equation 1. Where A is the area (J/g), MW is the average molecular weight of the side-chain repeat unit ((MW C18 x mol%) + (MW C22 x mol%)) and the result was multiplied by 1.25 to take into account the fact that the hydrophobic block represents only 75% of the BCP.…”