Multiblock Copolymers of l-Lactide and Trimethylene Carbonate

Abstract

Sequential copolymerizations of trimethylene carbonate (TMC) and l-lactide (LLA) were performed with 2,2-dibutyl-2-stanna-1,3-oxepane as a bifunctional cyclic initiator. The block lengths were varied via the monomer/initiator and via the TMC/l-lactide ratio. The cyclic triblock copolymers were transformed in situ into multiblock copolymers by ring-opening polycondensation with sebacoyl chloride. The chemical compositions of the block copolymers were determined from (1)H NMR spectra. The formation of multiblock structures and the absence of transesterification were proven by (13)C NMR spectroscopy. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and dynamic mechanical analysis (DMA) measurements confirmed the existence of a microphase-separated structure in the multiblock copolymers consisting of a crystalline phase of poly(LLA) blocks and an amorphous phase formed by the poly(TMC) blocks. Stress-strain measurements showed the elastomeric character of these biodegradable multiblock copolymers, particularly in copolymers having epsilon-caprolactone as comonomer in the poly(TMC) blocks.

Cyclic polymers: Synthetic strategies and physical properties

“…228,229 In addition to cyclic homopolyesters, cyclic copolyesters having random or block sequences were prepared. 207,[230][231][232][233][234][235][236][237][238] Cyclic diblock copolyesters were accessible in two ways. First, two lactones were polymerized in a sequential manner, under conditions preventing transesterification.…”

“…Multiblock copolymers consisting of flexible segments with low T g and of crystalline ''end segments'' are of interest as biodegradable thermoplastic elastomers. 230 Several publications deal with stabilization of the Bu 2 Sn-containing cyclic polyesters. The first approach illustrated in Scheme 51 is based on a ring exchange substitution quite analogous to that formulated for cyclic polyphthalates in Scheme 40 (3rd eq).…”

Aliphatic-aromatic poly(ester-carbonate)s obtained from simple carbonate esters, α,ω-aliphatic diols and dimethyl terephthalate

“…Usually polymers obtained by polycondensation exhibit poor mechanical properties due to relatively small molar mass. To obtain high molar mass poly(ester-carbonate)s copolymerization of cyclic esters (L-lactide, ε-caprolactone) with cyclic carbonate monomer-trimethylene carbonate (TMC) is usually carried out [12][13][14]. Besides TMC for copolymerization with cyclic esters other six-membered cyclic carbonates with different functional groups are also used [15][16][17][18].…”

Poly(CL/DLLA-b-CL) multiblock copolymers as biodegradable thermoplastic elastomers

“…Chain extension method in block copolymerization has formerly been utilized in the biopolymer group of our laboratory [3][4][5][6][7][8], and in some other groups [9][10][11]. The most widely used linking agents have been diisocyanates which combine hydroxyl terminated precursors to poly(ester-urethane)s. In addition to that, several research groups have prepared block copolymer structures by living ring-opening polymerization, or by something close to that, using pre-prepared macroinitiators (segment A) to initiate the ringopening polymerization of segment B [12][13][14][15][16]. Newer polymerization techniques, such as atom transfer radical polymerization (ATRP), have been utilized to make the control of the resulting block copolymer architecture more precise [17].…”

“…The use of conventional biopolymer monomers such as different lactones has been widely reported in literature [9][10][11][12][13][14][15][16][17]. Typically semi-crystalline poly(L-lactide) and poly(D-lactide) have been used as the hard blocks [9][10][11][12][13][14][15][16][17][18] while amorphous poly(ε-caprolactone) [10][11][12]18], poly(1,3-trimethylene carbonate) [13][14][15] and poly(ethylene oxide) [19] have been often used as soft components in block structured biodegradable TPEs. This study is natural continuum of the earlier work in the field of poly(ester-urethane)s carried by our biopolymer group in Helsinki University of Technology [1,[3][4][5][6][7].…”