Determination of domain sizes in heterogeneous polymers by solid‐state NMR

Abstract

Advanced solid-state NMR techniques exploiting 'H spin diffusion are described,which rely on selecting 'H magnetization of one of the components on the basis of 'H chemical shift or mobility differences under multiple-pulse irradiation. To monitor the progression of 'H spin diffusion, the higher resolution of I3C CP MAS spectra is exploited for NMR detection. For evaluation ofthe data,full quasi-analytical solutions ofthe diffusion equation as well as initial-rate approximations are derived, applied, and discussed. In order to obtain quantitative results, the 'H spin-diffusion constant has to be determined. To this end, the domain sizes in poly(styrene)-poly(methy1 methacrylate) systems including symmetrical diblock copolymers have been measured. The comparison of the NMR results with SAXS and TEM data yields the spin-diffusion coefficient for PS and PMMA.The resulting value ofD=0.8 nm2/ms is expected to be typical for rigid organic systems.The domain sizes investigated range from approximately 1 nm to ca. 100 nm. Bestimmung der DomanengroJen in heterogenen Polymeren mittels Festkorper-NMREs werden moderne Festkorper-NMR-Methoden beschrieben, die 'H-Spindiffusion ausnutzen und 'H-Magnetisierung einer der Komponenten des Systems auf Grund unterschiedlicher chemischer 'H-Verschiebung oder von Mobilitatsunterschieden bei Multipuls-Einstrahlung selektieren.Um die zeitliche Entwicklung der 'H-Spindiffusion zu ermitteln,wird fur den NMR-Nachweis die hohere Auflosung der "C-CP-MAS-Spektren ausgenutzt. Zur Auswertung der Ergebnisse werden vollstandige quasi-analytische Losungen der Diffusionsgleichung sowie Naherungen fur kurze Zeiten abgeleitet, angewendet und diskutiert. Um quantitative Ergebnisse zu erhalten, mu6 die 'H-Spindiffusionskonstante bestimmt werden. Zu diesem Zweck wurden die DomanengroRen in Poly(styren)-Poly(methylmethacry1at)-Systemen, einschliefllich symmetrischer Diblockcopolymere, gemessen. Ein Vergleich der NMR-Ergebnisse mit Rontgenkleinwinkelund elektronenmikroskopischen Daten ergibt als Wert des Spindiffusionskoeffizienten fur PS und PMMA D=0.8 nm2/ms, der als typisch fur starre organische Systeme angenommen werden darf. Die untersuchten DomanengroIJen liegen im Bereich von etwa 1 nm bis 100 nm.

Miscibility and Hydrogen Bonding in Blends of Poly(vinylphenol-co-methyl methacrylate) with Poly(ethylene oxide)

“…The maximum diffusive path length L can be estimated using the approximate eq 7. [29][30][31] For T 1F H of 5 ms and a effective spin diffusion coefficient, 32,33 we adopted the Painter-Coleman association model (PCAM) to predict thermodynamic properties. However, all the blends investigated in this study contain a self-associating polymer B and a nonself-associating polymer A, which can interact with B.…”

Spin diffusion and spin-lattice relaxation in multiphase polymers

“…Since it was first introduced by Goldman and Shen, 2 spin diffusion has been exploited by several research groups [3][4][5][6][7][8] to investigate the microphase structures in multiphase solid polymers. Polymers which display both crystalline and amorphous phases, 3,4,6,7 polymer blends, 5,9 block copolymers, 8,10,11 and core-shell polymers 12 have been investigated.…”

“…Polymers which display both crystalline and amorphous phases, 3,4,6,7 polymer blends, 5,9 block copolymers, 8,10,11 and core-shell polymers 12 have been investigated. Most of the above studies were based on the differences in molecular mobility in different phases.…”

“…More recently, selection techniques exploiting the differences in chemical shifts have also been introduced 13,14 and applied quite successfully. 8,9,14 The determination of domain sizes and interfacial thickness by spin diffusion is generally carried out through computer simulation. [6][7][8]15 Models that capture the essence of the spin diffusion process have been proposed.…”

“…8,9,14 The determination of domain sizes and interfacial thickness by spin diffusion is generally carried out through computer simulation. [6][7][8]15 Models that capture the essence of the spin diffusion process have been proposed. Packer and coworkers 6 discussed the spin diffusion and spin-lattice relaxations in a multiphase homopolymer.…”