@article {4271,
	title = {Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas},
	journal = {Journal of Controlled Release},
	volume = {52},
	number = {1-2},
	year = {1998},
	note = {ISI Document Delivery No.: ZC530Times Cited: 13Cited Reference Count: 11},
	month = {Mar},
	pages = {221-225},
	type = {Article},
	abstract = {In recent studies, NMR imaging has been used to investigate the swelling of hydroxypropylmethylcellulose (HPMC) tablets and to determine polymer concentration distributions in the swollen matrix. The total amount of polymer in the system was computed from these distributions and was up to 35\% greater than the known weight of HPMC in the tablet. This deviation was traced to the presence of air bubbles in the swollen matrix which occupied a significant volume previously assumed to be occupied by polymer and water. When the air in the tablet was removed by vacuum, the swollen gel contained no evidence of air bubbles and the calculated total polymer weights from the HPMC distributions were equal to the amount of HPMC in the tablet. (C) 1998 Elsevier Science B.V.},
	keywords = {BEHAVIOR, CONTROLLED RELEASE, DRUG-RELEASE, GEL, HPMC TABLETS, hydrophilic matrix tablet, hydroxypropylmethylcellulose, IMAGING METHOD, LAYER, MECHANISMS, NMR imaging, RELEASE DOSAGE FORMS, swelling},
	isbn = {0168-3659},
	url = {<Go to ISI>://000072589600022},
	author = {Fyfe, C. A. and Blazek, A. I.}
}
@article {3978,
	title = {Investigation of hydrogel formation from hydroxypropylmethylcellulose (HPMC) by NMR spectroscopy and NMR imaging techniques},
	journal = {Macromolecules},
	volume = {30},
	number = {20},
	year = {1997},
	note = {ISI Document Delivery No.: YA289Times Cited: 54Cited Reference Count: 21},
	month = {Oct},
	pages = {6230-6237},
	type = {Article},
	abstract = {NMR imaging has been used to investigate the in situ swelling behavior of 2-hydroxypropylmethylcellulose (HPMC) tablets in a sample geometry chosen for the simplicity of its diffusion behavior. Preliminary H-1 NMR spectroscopy experiments were performed on equilibrated mixtures of HPMC and water. From these, the dependence of the H-1 T-1 and T-2 relaxation parameters of the water protons with respect to HPMC weight percent were obtained. Further analysis of the T-2 values and H-1 z-spectroscopic data revealed that as the polymer concentration was increased from 10\% to 20\% w/w HPMC, the polymer mobility decreased substantially. One-dimensional NMR imaging of H-1 in the swelling tablet system was used to monitor the movement of water into the polymer and to calculate the T-2 parameters across the system. HPMC weight percents were calculated from these T-2 values using the previously determined calibration. HPMC distributions were determined for two tablet thicknesses. Similar swelling behavior was observed for both thicknesses at early times prior to the thinner tablet becoming completely hydrated.},
	keywords = {ABSORPTION, BEHAVIOR, DIFFUSION, DRUG-RELEASE, GEL LAYER, MECHANISMS, microscopy, PENETRATION, RELEASE DOSAGE FORMS, TABLETS},
	isbn = {0024-9297},
	url = {<Go to ISI>://A1997YA28900036},
	author = {Fyfe, C. A. and Blazek, A. I.}
}
