With a sting in its tail : An enantiopure neodymium complex (see scheme) acts as an efficient single‐site initiator for the controlled ring‐opening polymerization of rac‐lactide, forming isotactic polyester. The heteroscorpionate complex was characterized spectroscopically and by X‐ray diffraction.
Unmodified β‐cyclodextrin has been directly used to initiate ring‐opening polymerization of ϵ‐caprolactone in the presence of yttrium trisphenolate. Well‐defined cyclodextrin (CD)‐centered star‐shaped poly(ϵ‐caprolactone)s have been successfully synthesized containing definite average numbers of arms (Narm = 4–6) and narrow polydispersity indexes (below 1.10). The number‐average molecular weight ( ) and average molecular weight per arm ( ) are controlled by the feeding molar ratio of monomer to initiator. The prepared star‐PCL with of 2.7 × 103 is in fully amorphous and that with of 13.3 × 103 is crystallized. In addition, the obtained poly(e‐caprolactone) (PCL) stars with various molecular weights have different solubilities in methanol and tetrahydrofuran, which can be applied for further modifications. 相似文献
Methyl 2‐(bicyclo[3.1.0]hex‐1‐yl)acrylate ( 1 ) was synthesized from methyl 2‐(cyclopentene‐1‐yl)‐2‐hydroxyacetate by cyclopropanation, followed by oxidation to the corresponding bicyclic 2‐oxoacetate and Wittig olefination with methyltriphenylphosphonium bromide. Initiated with 2,2′‐azoisobutyronitrile at 65 °C in chlorobenzene, the radical homopolymerization of 1 occurred with opening of the cyclopropane ring leading to a polymer with a glass transition temperature of 90 °C. The reactivity of 1 in radical copolymerization was higher than that of methyl methacrylate.
The ring‐opening polymerization of two caprolactone monomers catalyzed by zinc undecylenate (ZU) is reported. Polymerizations were performed in bulk with benzyl alcohol (BnOH) as an initiator at 90 and 110 °C, respectively. A slower polymerization rate was observed for γ‐octyloxy‐ϵ‐caprolactone as compared to ϵ‐caprolactone. Diblock copolymers were synthesized by the sequential monomer addition at 90 and 110 °C. The kinetic studies performed for the ring‐opening polymerization of ϵ‐caprolactone and γ‐octyloxy‐ϵ‐caprolactone and the successful synthesis of diblock copolymers by the sequential monomer addition confirmed the controlled/living nature of zinc undecylenate catalyzed reactions. 相似文献
2‐Methylene‐1,3,6‐trioxocane (MTC) and 2‐methylene‐1,3‐dioxepane (MD) were synthesized and polymerized via ring‐opening in the presence of a radical initiator. The obtained poly(ester‐ether) (PMTC) and poly(ester) (PMD) were found to be enzymatically degradable by total organic carbon (TOC) analysis using lipase. The enzymatic degradability of PMTC was higher than that of PMD. PMTC and PMD were also found to be biodegradable with a biological oxygen demand (BOD)‐tester using soil. The degradability of PMTC using soil was also higher than that of PMD. The higher degradability of PMTC by enzyme and soil are thought to be due to its higher hydrophilicity. 相似文献
Ring‐opening metathesis polymerization (ROMP) of norbornene catalyzed by niobium(V) N,N‐dialkylcarbamates Nb(O2CNR2)5, R = Et ( 1 ), Me ( 2 ) was studied in the presence of methylaluminoxane (MAO) as a cocatalyst. These novel catalytic systems resulted very active in chlorobenzene: 1 in the presence of methylaluminoxane catalyzes the ROMP of norbornene with the highest activity (29 000 kg of polymer/mol of catalyst × hour) never reported up to now for niobium catalysts. The high productivity appears particularly attractive considering that these precursors are rather cheap and easy to synthesize and to handle. Polynorbornenes were characterized by FT‐IR and NMR spectroscopies and by DSC calorimetry. A new FT‐IR method for the swift determination of the cis/trans content of the polymer is presented.