Blends of aliphatic polyesters. VIII. Effects of poly(L‐lactide‐co‐ε‐caprolactone) on enzymatic hydrolysis of poly(L‐lactide), poly(ε‐caprolactone), and their blend films

Abstract

Poly(l-lactide), that is, poly(l-lactic acid) (PLLA), poly(-caprolactone) (PCL), and their blend (50/50) films containing different amounts of poly(l-lactide-co--caprolactone) (PLLA-CL), were prepared by solution casting. The effects of added PLLA-CL on the enzymatic hydrolysis of the films were investigated in the presence of proteinase K and Rhizopus arrhizus lipase by use of gravimetry. The addition of PLLA-CL decreased the proteinase K-catalyzed hydrolyzabilities of the PLLA and PLLA/PCL (50/50) films as well as the Rhizopus arrhizus lipase-catalyzed hydrolyzability of the PCL and PLLA/PCL (50/50) films. The decreased enzymatic hydrolyzabilities of the PLLA and PCL films upon addition of PLLA-CL are attributable to the fact that the PLLA-CL is miscible with PLLA and PCL and the dissolved PLLA-CL must disturb the adsorption and/or scission processes of the enzymes. In addition to this effect, the decreased enzymatic hydrolyzabilities of the PLLA/PCL (50/50) films upon addition of PLLA-CL can be explained by the enhanced compatibility between the PLLA-rich and PCL-rich phases arising from the dissolved PLLA-CL. These effects result in decreased hydrolyzable interfacial area for PLLA/PCL films. The decrement in proteinase K-catalyzed hydrolyzability of the PLLA film upon addition of PLLA-CL, which is miscible with PLLA, was in marked contrast with the enhanced proteinase K-catalyzed hydrolyzability of the PLLA film upon addition of PCL, which is immiscible with PLLA. This confirms that the miscibility of the second polymer is crucial to determine the proteinase K-catalyzed hydrolyzabilities of the PLLA-based blend films.

Immiscible Poly(L‐lactide)/Poly(ε‐caprolactone) Blends: Influence of the Addition of a Poly(L‐lactide)‐Poly(oxyethylene) Block Copolymer on Thermal Behavior and Morphology

“…[6] The driving force for compatibility was provided by the nature of the blocks, which were identical to the homopolymers, as confirmed also by the recent works of Tsuji et al on the addition of PLLA-PCL diblock copolymers to PLLA/PCL blends. [7,8] Moreover, the chain Summary: A binary blend of poly (L-lactide) (PLLA) and poly(e-caprolactone) (PCL) of composition 70:30 by weight was prepared using a twin screw miniextruder and investigated by differential scanning calorimetry (DSC), optical microscopy and scanning electron microscopy (SEM). Ternary 70:30:2 blends were also obtained by adding either a diblock copolymer of PLLA and poly(oxyethylene) (PEO) or a triblock PLLA-PCL-PLLA copolymer as a third component.…”

Enzymatic Degradation of Biodegradable Polyester Composites of Poly(L‐lactic acid) and Poly(ε‐caprolactone)

“…Among biodegradable polyester blends, those from glassy poly(Llactic acid) (PLLA) or poly(D,L-lactic acid) (PDLLA) with relatively low environmental degradability and rubbery poly(e-caprolactone) (PCL) with relatively high environmental degradability have attracted much attention because of their wide variety of physical properties and biodegradability. Numerous studies have been published for PLLA (or PDLLA)/PCL blends on the effects of polymer blending ratio, molecular characteristics, compatibilizers, coupling agents, and preparation methods and conditions of the blends on their morphology (phase structure), [3][4][5][6]8,9,11,[14][15][16][17][18][19][20][21][22][23][24][25][26][27] crystallization, [4][5][6]8,9,11,14,16,18,28,29] thermal, [2,4,8,9,15,17,18,21,23,24,26,28,29] mechanical, ...…”

“…[4,24] However, the addition of a compatibilizer reduces such drastic change and can improve the mechanical properties of the blends. [24] With respect to the enzymatic degradation of PLLA (or PDLLA)/ PCL blends, the effects of blending ratio, [12,17,19,20] compatibilizer, [25] and coupling agents [10] have been investigated. The following results were disclosed: (1) lipase-catalyzed enzymatic degradation of PCL chains was retarded by the presence of PLLA chains dissolved in PCL-rich domains for solution-cast blends; [19,25] (2) proteinase K-catalyzed enzymatic degradation of PLLA-rich domains was enhanced by the presence of PCL-rich domains neighboring on the PLLA-rich domains for solution-cast blends, [19,20] whereas disturbed for melt-processed blends; [10] (3) the addition of poly[(L-lactide)-co-(e-caprolactone)] as a compatibilizer between PLLA and PCL reduced lipase-or proteinase K-catalyzed enzymatic degradation rates of solution-cast blends; [25] (4) the coupling agents enhanced proteinase K-catalyzed enzymatic degradation of PLLA for the meltprocessed blends.…”

Application of Poly(hydroxyalkanoate) In Food Packaging: Improvements by Nanotechnology

“…This investigation indicates that this combination offers a new view for their industrial usage as short-term food packaging 12 . There are some effective solutions for mechanical problems, but some problems exist for barrier and thermal properties 11,12,[22][23][24][25][26] .…”