Cellulose Acetate‐graft‐Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer Composition

Abstract

Summary: Several different series of cellulose acetate‐graft‐poly(hydroxyalkanoate)s (CA‐g‐PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L‐lactide, (R,S)‐β‐butyrolactone, δ‐valerolactone and ε‐caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA‐g‐PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi‐empirical equations available for polymer blends or comb‐like polymers. In particular, the composition dependence of the Tgs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb‐like polymers, when CAs of acetyl DS ≈2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification.

Crystallization Behavior of Poly(ε‐caprolactone) Grafted onto Cellulose Alkyl Esters: Effects of Copolymer Composition and Intercomponent Miscibility

“…The data also indicate that the bulk copolymerization led to an adequate increase in the MS value, as expected, with an increase in the amount of in-fed CL monomer and/or with increasing reaction time period. As has been reported in previous studies, [11,14] the progression of this kind of CL polymerization using the Sn(II)Eht catalyst appears to follow a ''living-like'' manner. Table 2 summarizes thermal transition data for the graft copolymers explored in this study, together with the corresponding data for the original CAs and CBs as trunk polymer and a PCL homopolymer as a reference sample.…”

“…165 8C and a small melting endotherm at 258 8C, both signals originating from a phase-separated CA domain. This observation is reasonable, because the graft density along the backbone of CA 2.98 -g-PCL is quite low due to less amount of the residual hydroxyls and the product virtually behaves like a block copolymer, [11] which should induce such a phase separation of the originally immiscible, two components constituting the copolymer. In the case of CB 2.93 -g-PCL, contrastively, no segregation behavior was detected because the copolymer is composed of a pair of inherently miscible trunk and side-chain polymers.…”

“…[8,11] For the purpose of controlling the intramolecular graft density, the acyl DSs of CA and CB samples were varied. Taking an example of synthesis for CB-g-PCL, the typical procedure can be summarized as follows.…”

“…The CA-g-PHAs thus obtained were investigated to formulate a relationship between their molecular structures and thermal transition behaviors. [11] Especially for a CA-g-poly(L-lactic acid) series, Teramoto and Nishio [12] examined in detail the supramolecular structure development via quantitative estimations of physical aging and crystallization phenomena, in relation to the enzymatic degradation behavior. [9] In this extensional study, the graft copolymerization of e-caprolactone (CL) was applied to CA and CB, their acyl DS ranging from 2.1 to more than 2.9.…”

The Synthesis of Cellulose-graft-poly (L-lactide) by Ring-opening Polymerization and the Study of Its Degradability

“…[1][2][3][4] As the most abundant renewable natural biomass, cellulose offered a favourable combination of low cost, biodegradation, the ease of fiber surface modification, good mechanical properties, low density, and recyclability comparing with its inorganic counterparts. 5,6 However, there were also some challenges to the chemical modification of cellulose because of its high molecular weight, high crystallinity, rigidity of backbone chain and insolubility.…”