1. Drug–polymer interaction and its significance on the physical stability of nifedipine amorphous dispersion in microparticles of an ammonio methacrylate copolymer and ethylcellulose binary blend 
Jingjun Huang, Rodney J. Wigent, Joseph B. Schwartz 
Journal of Pharmaceutical Sciences 
Volume 97, Issue 1, Pages (January 2008)
DOI: /jps.21072
Copyright © 2008 Wiley-Liss, Inc. Terms and Conditions

2. Figure 1
Nifedipine microparticles (RL/EC = 2:1 w/w) with 14% w/w of drug loading by polarized light microscopy (magnification: 40×). Scale bar equals to 20 µm.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
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3. Figure 2
Evaluation of microparticle crystallinity by X‐ray powder diffraction. EC, untreated ethylcellulose N7 powder; RL, untreated Eudragit RL powder; %, drug loading (w/w), NIF, crystalline nifedipine.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
Copyright © 2008 Wiley-Liss, Inc. Terms and Conditions

4. Figure 3
DSC thermal analysis of nifedipine of different physical forms. ANIF, amorphous nifedipine; NIF, crystalline nifedipine; NIF + plain microparticles, the physical mixture of plain microparticles with 10% w/w of crystalline nifedipine.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
Copyright © 2008 Wiley-Liss, Inc. Terms and Conditions

5. Figure 4
DSC thermal analysis of nifedipine microparticles with different drug loadings. (A) DSC thermograms of microparticles. (B) Phase diagrams of microparticles estimated from the DSC thermal analysis; solid line in the phase diagrams (B) represents the glass transition point (Tg) of drug–polymer solid solution predicted by the Gordon–Taylor equation (Eq. (1)); ANIF, amorphous nifedipine; NIF, crystalline nifedipine; Tm1, melting temperature of solid nifedipine domains in microparticles; Tm2, melting temperature of crystalline nifedipine outside of microparticles.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
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6. Figure 5
Chemical structure and proposed hydrogen‐bonding sites between (A) nifedipine and nifedipine; (B) Eudragit RL (R1=CH3, H; R2=CH3, CH2CH3; R3=CH2CH2N+(CH3)4Cl−; R2:R3 ≅ 3:0.2 mole/mole) and nifedipine; (C) ethylcellulose and nifedipine; ‐‐‐ represents hydrogen bonding between functional groups.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
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7. Figure 6
Investigation of drug–polymer interactions by FTIR. (A) Microparticles of nifedipine solid dispersion with an EC and RL binary blend (RL/EC = 2:1) at different drug loadings. (B) Solid dispersion of nifedipine with a single polymer RL or EC (10% w/w). NIF, crystalline nifedipine; ANIF, amorphous nifedipine; NIFRL, solid dispersion of nifedipine with RL; NIFEC, solid dispersion of nifedipine with EC; EC, untreated ethylcellulose N7; RL, untreated Eudragit RL.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
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8. Figure 7
FTIR spectra of nifedipine amorphous dispersion with RL or EC (10% w/w) in a closed container after 3‐month stability storage at 40°C/75% relative humidity. NIFRL, nifedipine solid dispersion with RL; NIFEC, nifedipine solid dispersion with EC.
Journal of Pharmaceutical Sciences  , DOI: ( /jps.21072)
Copyright © 2008 Wiley-Liss, Inc. Terms and Conditions