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Chain‐linked lactic acid polymers with high molecular weight were synthesized by two‐step polymerization method, including polycondensation and chain extending reactions. The effects of chain extender toluene diisocyanate (TDI) on the chain‐linked lactic acid polymers were studied. The polymers obtained were characterized by gel permeation chromatography, fourier transform infrared spectroscopy, 1H NMR, and differential scanning calorimeter. Reactions between 1,4‐butanediol and lactic acid oligomers led to hydroxyl‐terminated prepolymer, which provided significant increase of molecular weight in the chain extending reaction. In addition, the glass transition temperature (Tg) and the melting temperature (Tm) were increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1045–1049, 2006

The linear and nonlinear shear rheological behaviors of poly(propylene) (PP)/clay (organophilic-montmorillonite) nanocomposites (PP/org-MMT) were investigated by an ARES rheometer. The materials were prepared by melt intercalation with maleic anhydride functionalized PP as a compatibilizer. The storage moduli (G'), loss moduli (G"), and dynamic viscosities of polymer/clay nanocomposites (PPCNs) increase monotonically with org-MMT content. The presence of org-MMT leads to pseudo-solid-like behaviors and slower relaxation behaviors of PPCN melts. For all samples, the dependence of G' and G" on ω shows nonterminal behaviors. At lower frequency, the steady shear viscosities of PPCNs increase with org-MMT content. However, the PPCN melts show a greater shear thinning tendency than pure PP melt because of the preferential orientation of the MMT layers. Therefore, PPCNs have higher moduli but better processibility compared with pure PP.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2427–2434,2004