High Molecular Weight Poly (L-lactic Acid) Clay Nanocomposites Via Solid-State Polymerization
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Title |
High Molecular Weight Poly (L-lactic Acid) Clay Nanocomposites Via Solid-State Polymerization
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Creator |
KATIYAR, V
NANAVATI, H |
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Subject |
RING-OPENING POLYMERIZATION
LAYERED SILICATE NANOCOMPOSITES POLY(L-LACTIC ACID) MELT/SOLID POLYCONDENSATION CRYSTALLIZATION CELLULOSE POLY(EPSILON-CAPROLACTONE) POLYLACTIDE BEHAVIOR PLLA |
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Description |
We propose here, a novel technique to synthesize high molecular weight (MW) poly (L-lactic acid)-clay nanocomposite (PLACN), via solid state polymerization (SSP). We synthesize prepolymer of PLACN (pre-PLACN) from both, L-lactic acid and L-lactide, as starting materials. Synthesis of pre-PLACN from L-lactic acid is carried out via in situ melt polycondensation (MP) of L-lactic acid oligomer, followed by SSP, to achieve high MW PLACN (M(w) similar to 138,000 Da). In case of L-lactide as the starting material, we prepare L-lactide-clay intercalated mixture which yields moderate MW pre-PLACN during subsequent ring opening polymerization (ROP). Interestingly, ROP is performed by using hydroxyl functionalized ternary catalyst system (L-lactide Sn(II) octoate oligo (L-lactic acid) complex), which provides the terminal hydroxyl end-groups, required for step-growth SSP. Pre-PLACN MW is now increased to M(w) similar to 127,000 Da, by the subsequent SSP process. (1)H NMR analyses confirm that these end-groups, are indeed consumed during SSP. During SSP, the PLACN also achieves up to 90% crystallinity, which may be due to the synchronization of the slow step-growth SSP of poly(L-lactic acid) (PLA) with the crystallization kinetics. Optical purity of PLACNs is similar to that of neat PLA, whereas the thermal stability of PLACNs is significantly superior. As evidenced by wide-angle X-ray scattering/small-angle X-ray scattering analyses and in line with the literature, both, intercalated and exfoliated PLACN morphologies, have been synthesized, by suitable selection of clays. We also verify the correlation between the PLA semicrystalline morphology and the PLACN morphology, which is consistent with those of PLACN synthesized by other techniques. POLYM. COMPOS., 32:497-509,2011. (C) 2011 Society of Plastics Engineers
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Publisher |
WILEY-BLACKWELL PUBLISHING, INC
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Date |
2012-06-26T04:55:30Z
2012-06-26T04:55:30Z 2011 |
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Type |
Article
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Identifier |
POLYMER COMPOSITES,32(3)497-509
0272-8397 http://dx.doi.org/10.1002/pc.21069 http://dspace.library.iitb.ac.in/jspui/handle/100/13916 |
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Language |
English
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