Miscible blends of perdeuteriopoly(ethylene oxide) (d4PEO) and poly(methyl methacrylate) (PMMA) were studied using deuterium NMR over the concentration range of 0.5−30% d4PEO using 2−4 Larmor frequencies ranging from 31 to 76 MHz. Spin−lattice relaxation times and line widths were measured from 300 to 475 K. Over this range PEO is liquidlike or rubbery in terms of its dynamics even though many of the measurements are below the blend glass transition temperature. There is no indication of the DSC glass transition in terms of a jump in either the spin−lattice relaxation times or the line widths. A model suitable for a rubber solid was used to interpret the spin−lattice relaxation times in terms of segmental motion and backbone libration. Segmental correlation times for d4PEO fall in the nanosecond range with a very broad distribution of correlation times described by a KWW β of about 0.27. The segmental dynamics of d4PEO are 12 orders of magnitude faster than PMMA segmental dynamics for a 3% d4PEO blend near the blend T g. Over the temperature range studied, d4PEO segmental dynamics are nearly independent of composition for blends from 0.5% to 30% d4PEO. At the lowest concentration studied, d4PEO is in the dilute solution range; this eliminates intermolecular concentration fluctuations as an explanation of the rapid d4PEO dynamics. These observations are unusual for miscible polymer blends and cannot be described by current models.

The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water-and fat-suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density. The phantom contained a specifically designed poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend, whose MRI properties (T 1 , T 2 , and resonance linewidth) were similar to those of solid bone matrix (collagen, tightly bound water, and other immobile molecules), minimizing the need to correct for differences in T 1 and/or T 2 relaxation between the phantom and the subject. Cortical and trabecular porcine bone specimens were imaged using WASPI with the calibration phantom in the field of view (FOV) as a stable intensity reference. Gravimetric and amino acid analyses were carried out on the same specimens after WASPI, and the chemical results were found to be highly correlated (r 2 ‫؍‬ 0.98 and 0.95, respectively) to the WASPI intensity. By this procedure the WASPI intensity can be used to obtain the true bone matrix mass density in g cm -3 .

In this study, bone mineral density (BMD) of normal (CON), ovariectomized (OVX) and partially nephrectomized (NFR) rats was measured by 31 P NMR spectroscopy; bone matrix density was measured by 1 H water-and fat-suppressed projection imaging (WASPI); and the extent of bone mineralization (EBM) was obtained by the ratio of BMD/bone matrix density. The capability of these MR methods to distinguish the bone composition of the CON, OVX and NFR groups was evaluated against chemical analysis (gravimetry). For cortical bone specimens, BMD of the CON and OVX groups was not significantly different; BMD of the NFR group was 22.1% (by 31 P NMR) and 17.5% (by gravimetry) lower than CON. For trabecular bone specimens, BMD of the OVX group was 40.5% (by 31 P NMR) and 24.6% (by gravimetry) lower than CON; BMD of the NFR group was 26.8% (by 31 P NMR) and 21.5% (by gravimetry) lower than CON. No significant change of cortical bone matrix density between CON and OVX was observed by WASPI or gravimetry; NFR cortical bone matrix density was 10.3% (by WASPI) and 13.9% (by gravimetry) lower than CON. OVX trabecular bone matrix density was 38.0% (by WASPI) and 30.8% (by gravimetry) lower than CON, while no significant change in NFR trabecular bone matrix density was observed by either method. The EBMs of OVX cortical and trabecular specimens were slightly higher than CON but not significantly different from CON. Importantly, EBMs of NFR cortical and trabecular specimens were 12.4% and 26.3% lower than CON by 31 P NMR/WASPI, respectively; and 4.0% and 11.9% lower by gravimetry. Histopathology showed evidence of osteoporosis in the OVX group and severe secondary Corresponding Author: Yaotang Wu, Department of Orthopaedic Surgery, Children's Hospital, Room 930, Enders Building, 300 Longwood Avenue, Boston, MA 02115, Phone: 617-919-2060, Fax: 617-730-0122, yaotang.wu@childrens.harvard.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptBone. Author manuscript; available in PMC 2011 June 1.