Determination of Block Copolymer Micelle Core T_g Using ¹H NMR Transverse (T₂) Relaxation Measurements of Micelle Coronas

Abstract

The dynamic properties of poly(ethylene glycol) (PEG) corona chains in block copolymer (BCP) micelles were investigated with 1 H nuclear magnetic resonance (NMR) spectroscopy. The 1 H NMR spectra of BCP micelles show the PEG peak is significantly broadened, which suggests a difference in mobility in PEG segments near to the core and far from the core. 1 H NMR transverse (T 2 ) relaxation measurements suggest that the overall mobility of the PEG chains in BCP micelles is about 5−10 times slower than that of the fully hydrated PEG segments and is significantly influenced by the glass transition of the micelle core domain. The micelle core glass transition causes an increase in the Arrhenius activation energy, suggesting that the rigid nature of the core domain below T g increases the energy barrier of rotation of the PEG near to the core domain. Therefore, this study establishes that corona T 2 measurements can be used to determine the micelle core T g .

Effect of temperature on the air–water surface mechanical behavior of water-spread block copolymer micelles

“…The two techniques are described in more detail in separate manuscripts. 14,16 The first technique is the use of the molecular rotor, farnesyl-(2-carboxy-2-cyanovinyl)-julolidine (FCVJ), to measure local viscosity/free volume changes in the core domain. The FCVJ compound is encapsulated in the core domain and the fluorescence is measured as a function of temperature.…”

“…14,15 Herein, we study the air–water surface mechanical behavior of water-spread PS-PEG and PtBMA-PEG micelles at various temperatures above and below their respective core T g values. The core T g values were previously characterized by both an 1 H NMR technique 16 (which predicts the core T g of the outer core domain) and a molecular rotor technique 14 (which predicts the mean core T g of the entire core volume). The surface mechanical behavior is characterized using Langmuir trough surface pressure–area isotherms as well as quantitative Brewster angle microscopy (QBAM).…”

Surface Mechanical Behavior of Water-Spread Poly(styrene)–Poly(ethylene glycol) Cylindrical Micelles at the Air–Water Interface

“…PLS distinguishes itself by avoiding disruption caused by protein-rich exudate and inflammation, making it a promising therapy for respiratory disorders, particularly ARDS. , Our prior research efforts have highlighted the suitability of poly­(styrene)- block -poly­(ethylene glycol) (PS–PEG) for applications in PLS. , PS–PEG micelles exhibit high surface pressure (Π > 60 mN/m) and reliable respreading at the air–water interface during repeated compression and expansion cycles, satisfying the Laplace stability criterion . The efficacy of PS–PEG micelles in mitigating lung dysfunction was effectively demonstrated through successful in vivo experiments. , These positive results have prompted further investigations into the fundamental properties governing the air–water interface behavior of PS–PEG micelle systems. − …”