Determination of Particle Size Distributions, Molecular Weight Distributions, Swelling, Conformation, and Morphology of Dilute Suspensions of Cross-Linked Polymeric Nanoparticles via Size-Exclusion Chromatography/Differential Viscometry

Abstract

Size-exclusion chromatography (SEC), coupled with differential viscometry detection (SEC/DV), is applied to the dilute suspension characterization of solvent-swollen cross-linked polymeric nanoparticles (PNPs). Cross-linked, unimolecular polymeric nanoparticles in the 5−50 nm weight-average diameter (d w ) range were prepared by batch and semibatch microemulsion polymerization techniques and isolated. SEC and SEC/DV characterization techniques yield, based on the principle of universal calibration, a wealth of information regarding the structural attributes of PNPs, including apparent and absolute molecular weight distributions, apparent and absolute molecular weight averages, peak and weightaverage particle diameters, particle size distributions in both the solvent-swollen and solvent-free states, particle conformation (shape), and an estimate of the volumetric swell factor. These structural parameters are critical to understanding PNP performance, and all are obtained in a single rapid chromatographic experiment, when conducted under conditions where universal calibration applies. Particle sizes determined under such conditions are in excellent agreement with those obtained by dynamic light scattering, transmission electron microscopy, hydrodynamic chromatography, and SEC/static light scattering (SEC/SLS). In addition, Mark−Houwink exponents of approximately zero were found across the molecular weight and size distribution of many of these tightly cross-linked PNPs, which is consistent with a spherical particle conformation in these dilute suspensions. The SEC/DV methods are especially valuable to characterize the diameter, volume swell factor, and suspension conformation of small (4−5 nm d w ) PNPs.

Thermal Field-Flow Fractionation with Quintuple Detection for the Comprehensive Analysis of Complex Polymers

“…However, aggregations and cross-linked polymeric nanoparticles have also been shown to exhibit the same trait, where the characteristic M w independent behavior of [η] is observed. , To get more explicit topological information, the ratio R g / R h (ρ) which is naturally independent of M w is employed. A value of ∼1.31 is obtained that infers the existence of hyperbranched polymers. , Moreso, similar values have been reported for vesicle-like structures …”

“…The addition of an online viscometer (dVis) to other information-rich detectors enables the online measurement of absolute M w , CCs, R h , viscosity-based sizes ( R gη and R η ), and [η] for complex polymers and ultimately for SAs. [η] and the respective sizes can subsequently be used to derive information on molecular density, shape, and structure of SAs as well as their respective distributions. − In general, online viscometry is applied in polymer analysis when investigating branching and branching distributions. − By conceptualizing the aggregation number ( Z ) as a form of branching, SAs can in principle be regarded as pseudobranched materials. To some point their solution properties can be expected to exhibit parallel trends with branched materials.…”

A Useful Methodology for Determining the Compaction Degree of Single‐Chain Nanoparticles by Conventional SEC

“…Reliable SEC data corresponding to swollen globules having φ = 0.5 are summarized in Table . From these experimental data, the M app / M ratio can be easily computed and compared to the predicted one for swollen globules (Equation , φ = 0.5), as illustrated in Figure A (green solid triangles).…”

“…Unfortunately, absence of Ð data in ref. (only Ð app was reported) does not allow one to provide a comparison of experimental and theoretical Ð app / Ð ratios in Figure B.…”

“…Table 2 shows a comparison of data calculated from Equation to experimental data for swollen PS globules having φ ≈ 0.5 (data taken from Ref. ).…”