Via an isocyanate-free route, a series of segmented polyureas (PUs) were synthesized from (potentially) renewable resources. To the best of our knowledge, the present work shows for the first time that the organic superbase guanidine 1,5,7-triazabicyclododecene (TBD) which was originally developed as a catalyst for the ring-opening polymerization of lactones, lactides or cyclic carbonates, is also a promising catalyst for the transurethanization between dicarbamates and diamino-terminated poly(propylene glycol) (PPGda) providing PUs via an isocyanate-free strategy. The renewable segmented PUs contain monodisperse hard segments (HSs). This well-defined structure was verified by the DMTA plots of the PUs, showing a sharp glass transition, a sharp flow transition and a flat rubbery plateau. The flow and maximum use temperature (Tfl ) of the PUs increases with the increasing number of urea groups in the corresponding dicarbamates. In addition, at constant HS length, the length of the soft-segment (SS) can be changed to adjust the properties of the PU materials, enabling their application as adhesives, soft elastomers, or rigid plastics.

No abstract

No abstract

Using the organic compound 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) as a catalyst for step‐growth polymerization, a series of well‐defined hydroxyl‐telechelic renewable aliphatic polyesters (including poly(1,3‐propylene adipate); poly(1,4‐butylene adipate); poly(1,12‐dodecylene sebacate); and poly(1,2‐dimethylethylene adipate), PDMEA) were synthesized and studied. PDMEA is a novel polyester, which has not been reported before. The results of 1H NMR and Matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry indicate that the polymers are fully hydroxyl terminated. From differential scanning calorimetry (DSC) thermograms, we found that the glass transition temperatures (Tg) of these polyesters are below −20 °C. Only a Tg but no melting peak is observed in the DSC curve of the novel PDMEA. This indicates that PDMEA, contrary to the other renewable polyesters, is totally amorphous. Furthermore, using hexamethylene diisocyanate and hexamethylene diamine, poly(ester urethane urea)s (PEUUs) based on PDMEA were successfully synthesized. The Tg of the prepared PEUUs is below 0 °C, and no melting behavior of the soft‐segment is observed. The PEUU, with a flow temperature of over 200 °C, thus behaves as an elastomer at room temperature. Its mechanical properties, such as a relatively low tensile E‐modulus (≈20 MPa) at room temperature and a sufficiently high strain at break (≈560%), make it suitable for use in, for example, biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Copolymerizations of n-butyl methacrylate (BMA) and fluoro-methacrylates (including 2,2,3,4,4,4-hexafluorobutyl methacrylate, HFBMA and 2,2,2-trifluoroethyl methacrylate, TFEMA) were carried out via reversible addition-fragmentation chain transfer miniemulsion polymerization, using cumyl dithiobenzoate as a chain transfer agent. The experimental results show that the copolymerizations exhibit ''living'' fashion, with controlled molecular weights and narrow polydispersities. The reactivity ratios of BMA and fluoromethacrylate in this kind of polymerization system were investigated by size exclusion chromatography and nuclear magnetic resonance, from which the Q-and e-values of HFBMA and TFEMA were calculated. Compared with its corresponding non-fluoric methacrylate, fluorinated methacrylate exhibits higher resonance stability of the radical adducts. The Q-value of fluorinated methacrylate is higher (Q BMA ¼ 0.82 to Q HFBMA ¼ 1.70 and Q EMA ¼ 0.76 to Q TFEMA ¼ 1.01), and e-value is much larger (e BMA ¼ 0.28 to e HFBMA ¼ 1.24 to and e EMA ¼ 0.17 to e TFEMA ¼ 1.29) for its rather unique high electron-withdrawing inductive effect of the fluoroalkyl ester group. The thermal property and the wetting property of copolymers were also discussed. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5067-5075, 2007

A novel furfural-based DOPO-containing flame retardant MBF-DOPO was successfully synthesized and acted as a co-curing agent for fire-safe epoxy resins.

No abstract

As one of the environmental problems, 'white pollution' is caused by the accumulation of nondegradable polymer materials. Recycling is one solution, however, creating biodegradable polymers would be more feasible for many applications. 1-6 If those biodegradable polymers exhibit similar properties to the nonbiodegradable ones then they should be more commercially competitive. 7-9 Among those biodegradable polymers developed so far, aliphatic polyesters are the best-known and they are already widely utilized in many applications (e.g., drug delivery carriers, medical implants, and tissue scaffolding) 10-15 since the ester linkages in aliphatic polyesters are hydrolytically or enzymatically degradable. 16,17 However, most of the biodegradable aliphatic polyesters exhibit low melting temperatures (T m ) and subpar mechanical properties. For instance, the T m of poly(e-caprolactone) is around 60 8C. 18 On the contrary, aromatic polyesters have high T m values (e.g., the T m of polyethylene terephthalate is as high as 260 8C 19 ) and show competitive mechanical properties but they are typically nonbiodegradable.The aim of this study is to bridge the gap between the aliphatic and the aromatic polyesters and to create biodegradable polymers with higher T m values. Inclusion of the urethane or urea group into polymer backbones can enhance the crystallization/aggregation of polymer chains. 20 Furthermore, urea groups can also be degraded by proteases, such as papain. 21,22 Therefore, we explored a class of polymer, namely poly(urea ester)s (PUEs), via polycondensation of dimethyl esters (DMEs) and di(hydroxyalkyl) urea (DHAU, Scheme 1). In a PUE polymer chain, the ester groups offer biodegradability while the urea groups provide hydrogenbonding which should increase the T m and/or enhance the performance. Mulhaupt and co-workers reported previously the preparation of PUEs based on polyether polyols through an N,N 0 -carbonylbiscaprolactam route but only crosslinked materials were prepared. 23 Du et al. also synthesized nonbiodegradable liquid crystalline PUEs. 24 To the best of our knowledge, this work would be the first one creating biodegradable thermoplastic PUE.Since amino groups react with urea at elevated temperatures and hydroxy groups are much less reactive, 25 we posited that DHAUs could possibly be prepared from amino alcohols (AAs) and urea. A series of DHAUs with different alkylene lengths between the urea group and the hydroxy group were prepared: DHAU-4, DHAU-5, and DHAU-6 (Scheme 1). The reactions of urea with 4-amino-1-butanol (AA-4), 5-amino-1pentanol (AA-5), and 6-amino-1-hexanol (AA-6) were performed at 150 8C. In all these reactions the conversions were essentially quantitative within 24 h. The crude products were precipitated in acetone to remove the monosubstituted by-products and the remaining AAs. The isolated yields of DHAUs were all around 80%. The melting points of these DHAUs range from 110 to 128 8C.By transesterification polymerization, DHAUs react with DMEs to form PUEs (Scheme 1). It is of ...