A one-pot, one-catalyst, sequential ring-opening transesterification polymerization (ROTEP) was used to prepare fully renewable amorphous poly(D,L-lactide)−poly(ε-decalactone)−poly(D,L-lactide) (LDL) triblock polymers. These α,ω hydroxy-telechelic polymers were subsequently coupled to prepare linear alternating (LDL) n multiblock polymers. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) indicated microphase separation into two domains in both the triblock and multiblock architectures. The temperature dependent Flory−Huggins interaction parameter for this system, χ(T) = 69.1/T − 0.072, was estimated from the experimentally determined order−disorder transition temperature (T ODT ) values of four symmetric LDL triblock polymers. Uniaxial extension tests revealed a dramatic dependence of the room-temperature mechanical properties on overall molar mass. Additionally, coupling low molar mass LDL triblocks to prepare (LDL) n multiblocks led to substantial increases in the ultimate elongation and tensile stress at break. Compared to high molar mass triblocks with inaccessible T ODT values, (LDL) n multiblocks of similar composition and molar mass were found to disorder at much lower temperatures (T ODT < 150°C). Because of this, it was possible to process (LDL) n using injection molding. The simple synthetic procedure and melt processability of the (LDL) n multiblock polymers make these multiblocks attractive as renewable thermoplastic elastomers (TPEs).

ABA triblock copolymers were prepared using the renewable monomers menthide and lactide, by sequential ring-opening polymerizations. Initially, hydroxy telechelic polymenthide was synthesized by the diethylene glycol-initiated and tin(II) ethylhexanoate-catalyzed polymerization of menthide. The resulting 100 kg mol−1 polymer was used as a macroinitiator for the tin(II) ethylhexanoate-catalyzed ring-opening polymerization of d,l-lactide. Two polylactide−polymenthide−polylactide triblock copolymers were prepared with 5 and 10 kg mol−1 polylactide end blocks. Transesterification between the two blocks, and polylactide homopolymer formation were minimized, and triblock copolymers with narrow molecular weight distributions were produced. Microphase separation in these systems was corroborated by differential scanning calorimetry and small-angle X-ray scattering measurements. The triblocks were combined with up to 60 wt % of a renewable tackifier, and the resulting mixtures were evaluated using probe tack, 180° peel adhesion, and shear strength tests. Maximum values of peel adhesion (3.2 N cm−1) and tack (1.1 N) were obtained at 40 wt % of tackifier. These new materials hold promise as renewable and hydrolytically degradable pressure-sensitive adhesives.

Amorphous ABA type block aliphatic polyesters can be useful as degradable and biorenewable thermoplastic elastomers. These materials can be prepared by sequential ringopening transesterification polymerization (ROTEP) reactions and can exhibit a range of physical properties and morphologies. In this work a set of amorphous polylactideÀpoly(6-methyl-ε-caprolactone)Àpolylactide aliphatic polyester ABA triblock copolymers were prepared by consecutive controlled ring-opening polymerizations. Ring-opening polymerization of neat 6-methyl-εcaprolactone in the presence of 1,4-benzenedimethanol and tin(II) octoate afforded α,ω-hydroxyl-terminated poly(6-methyl-εcaprolactone). High conversions of 6-methyl-ε-caprolactone (>96%) afforded polymers with molar masses ranging from 12 to 98 kg mol À1 , depending on monomer-to-initiator ratios, polymers with narrow, monomodal molecular weight distributions. An array of polylactideÀpoly(6-methyl-ε-caprolactone)Àpolylactide triblock copolymers with controlled molecular weights and narrow molecular weight distributions were synthesized using the telechelic poly(6-methyl-ε-caprolactone) samples as macroinitiators for the ring-opening polymerization of D,L-lactide. The morphological, thermal, and mechanical behaviors of these materials were explored. Several triblocks adopted well-ordered microphase-separated morphologies, and both hexagonally packed cylindrical and lamellar structures were observed. The FloryÀHuggins interaction parameter was determined, χ(T) = 61.2T À1 À 0.1, based on the order-to-disorder transition temperatures of two symmetric triblocks using the calculated mean field theory result. The elastomeric mechanical behavior of two high molecular weight triblocks was characterized by tensile and elastic recovery experiments.

The bulk ring-opening polymerization of renewable δ-decalactone using 1,5,7-triazabicyclo[4.4.0]dec-5ene was carried out at temperatures between 7 and 110 °C. The equilibrium monomer concentration for reactions within this temperature range was used to determine the polymerization thermodynamic parameters (ΔH p = −17.1 ± 0.6 kJ mol −1 , ΔS p = −54 ± 2 J mol −1 K −1 ) for δ-decalactone. The polymerization kinetics were established and high molar mass poly(δ-decalactone) was prepared with a glass transition temperature of −51 °C. Poly(δ-decalactone) samples with controlled molar mass and narrow molar mass distributions were realized by controlling the monomer conversion and initiator concentration. A high molar mass poly(lactide)-poly(δ-decalactone)-poly(lactide) triblock copolymer with a low polydispersity index was prepared by simple sequential addition of monomers. The product triblock exhibited two distinct glass transitions temperatures consistent with microphase segregation.

Batch ring opening transesterification copolymerization of ε-caprolactone and ε-decalactone was used to generate statistical copolymers over a wide range of compositions and molar masses. Reactivity ratios determined for this monomer pair, r CL = 5.9 and r DL = 0.03, reveal ε-caprolactone is added preferentially regardless of the propagating chain end. Relative to poly(ε-caprolactone) the crystallinity and melting point of these statistical copolymers were depressed by the addition of ε-decalactone; copolymers containing greater than 31 mol% (46 wt%) ε-decalactone were amorphous. Poly(lactide)-block-poly(ε-caprolactone-co-ε-decalactone)-block-poly(lactide) triblock polymers were also prepared and used to explore the influence of midblock composition on the temperature dependent Flory-Huggins interaction parameter (χ). In addition, uniaxial extension tests were used to determine the effects of midblock composition, poly(lactide) content, and molar mass on the mechanical properties of these new elastomeric triblocks.H NMR Spectra, 13 C NMR Spectra, DMA Data, DSC Data, Hysteresis Data and SAXS spectra are also provided in Tables S1-S12 and Fig. S1-S25. See