Poly ester urethane s

Since poly(ester) poly(urethane)s bear ester groups they are likewise subject to hydrolytic degradation (5). 

It has been shown that hydrolysis can play a significant role in the aging of these materials (6). Moreover, the ester segments are much more susceptible to hydrolytic a cleavage than the urethane 

In addition, poly(urethane)s and segmented polyfurethane urea)s derived from lysine diisocyanate, can be enzymatically degraded by various proteases. Thiol proteases, such as papain, bromelain, and ficin, show a high activity. In addition, protease K and chymotrypsin hydrolyze the poly(urethane)s (9). 

Hydrol)dic stabilizers can be included in poly(ester) poly(ol) based poly(urethane)s. Two commercially available carbodiim-ide based hydrolytic stabilizers are known as Stabaxol P and Stabaxol P-100. They are available from Rhein Chemie of Trenton, N.J., and are effective at reducing the susceptibility of the material to hydrolysis (5). 

Still other hydrolytic stabilizers, such as those which are carbodi-imide or poly(carbodiimide) based, or based on epoxidized soy bean oil, are considered useful. The total amount of hydrolytic stabilizer employed will generally be less than 5.0% of the composition (10). 

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Another approach was attempted by Seppala and Kylma who reported the synthesis of poly(ester-urethane)s by condensation of hydroxyl terminated tel-echelic poly(CL-co-LA) oligomers with 1,6-hexamethylene diisocyanate (Scheme 33) [94]. The diisocyanate acts as chain extender producing an increase in molecular weight of the preformed oligomers. The authors claim that some of the copolymers present elastomeric properties. Using a similar method. Storey described the synthesis of polyurethane networks based on D,L-LA, GA, eCL,... 

Keywords. Monomers from renewable resources, Polymers from renewable resources, 1,3-Propanediol, Succinic acid, Lactones, Cyclohexanedimethanol, Polyethyleneglycol, Chain-extension, Poly(ester-urethane)s, Poly(ester-carbonate)s... 

PEU Poly(ester-urethane)s PHB Poly-(3-hydroxybutyrate ROP Ring-opening polymerization SEC Size exclusion chromatography SP Oligo(l,3-propylene succinate)... 

Two different types of chain-extending agents were used, namely 4,4 -di-isophenylmethane diisocyanate (MDI) and phosgene, which lead to two different classes of copolymers, poly(ester-urethane)s and poly(ester-carbonate)s respectively. High molecular weight poly(ester-carbonate)s have earlier been prepared by the dichloroformate synthesis [12-13]. 

Table 3. Molecular weights of poly(ester urethane)s ...

The series of ten different segmented poly(ester-urethane)s obtained was characterized by SEC (molecular weight, polydispersity), DMA (thermo-mechanical properties), DSC (thermal properties) and Instron (mechanical properties). Before the mechanical testing could be performed, it was necessary to establish procedures for film production. 

The basic structure of these poly(ester urethane)s with a DAAB derivative randomly incorporated in the polyester soft segment in various concentrations is shown in Fig. 7. 

Eisenbach CD. 1980a. Cis trans isomerization of aromatic azo chromophores, incorpo rated in the hard segments of poly(ester urethane)s. Macromol Rapid Commun 1(5) 287 292. 

Hiltunen, K., Seppl, J. V., and Hrkonen, M. (1997). Lactic acid based poly(ester-urethane)s The effects of different polymerization conditions on the pol mier structure and properties. 

B. F. Pierce, A. H. Brown and V. V. Sheares, Thermoplastic poly (ester urethane)s with novel soft segments , Macromolecules, 2008,41,3866-73. 

However, PLA can be pol5merized with diisocyanates to form poly(ester-urethane)s or with caprolactones to form poly(L-lactic acid-co-e-caprolactone-urethane)s. Such copolymers can be tailored as hard plastics or flexible elastomers and can have unique glass transition temperatures from -70°C to +60°C, tensile modulus from 2 MPa to 2000 MPa, and % strain from 1% to about 1000% (2). 

Figure 4.2 Synthesis of a,tB-hydro3g l polylactide pre-pol3Tner initiated by 1,4-butanediol (a) or 4,4 -diaininodiphenylmethane (b) and qmthesis of poly(ester-urethane)s by chain extension reaction (c) (adapted and used...

Nuclear magnetic resonance (NMR) spectroscopy is one of the other basic methods for structural analysis. Aluri et al. [16] proposed a one-pot synthesis route to obtain two polymers of ABB for linear polyester and hyperbranched poly(ester-urethane)s based on multifunctional L-amino acid monomers using a temperature-selective melt... 

R. Aluri, M. Jayakannan, One-pot two polymers ABB melt polycondensation for linear polyesters and hyperbranched poly(ester-urethane)s based on natural 1-amino acids. Polymer Chemistry 6 (25) (2015) 4641-4649. 

In a similar approach, our group synthesised two biodegradable poly(ester urethane)s from PCL macrodiol and 1,4-diisocyanatobutane (SUvestti et al., 2014). The PURs differed in the chain extenders, which were L-lysine ethyl ester and AAK. The PUR containing the peptide sequence showed a higher weight loss in elastase solution. 

On W, Qiu H, Chen Z, Xu K. Biodegradable block poly(ester-urethane)s based on poly (3-hydroxybutyrate-co-4-hydroxybut5Tate) copolymers. Biomateiials April 2011 32(12) 3178-88. 

Caracciolo PC, Thomas V, Vohra YK, Buffa F, Abraham GA. Electrospinning of novel biodegradable poly(ester urethane)s and poly(ester urethane urea)s for soft tissue-engineering applications. J Mater Sci Mater Med October 2009 20(10) 2129-37. 

Loh XJ, Tan YX, Li Z, Teo LS, Goh SH, Li J. Biodegradable thermogelling poly(ester urethane)s consisting of poly(lactic acid)-thermodynamics of micellization and hydrolytic degradation. Biomaterials 2008 29(14) 2164-72. 

Chen ZF, Cheng ST, Xu KT. Block Poly(ester-urethane)s based on poly(3-hydroxybu-tyrate-co-4-hydroxybutyrate) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate). Biomaterials 2009 30(12) 2219-30. 

George and Barrie have extended their studies of the metallation of polymers to polyurethanes. Poly(ester-urethane)s based on diphenyl methane-4,4-di-iso-cyanate and toluene di-isocyanate were metallated with sodium hydride in THF. Metallation apparently occurs at the urethane link (Scheme 18) and these O... 

Chain extension with diisocyanates is undoubtedly the most commonly applied chain-extension approach for aliphatic polyesters (Figure 3.4). A large number of different diisocyanates have been used as linking molecules in the preparation of aliphatic poly(ester-urethane)s. Various isocyanates are listed in Table 3.1 together with the t) e of prepolymer used. 

The most frequently used diisocyanate in the preparation of aliphatic poly(ester-urethane)s is 1,6-hexamethylene diisocyanate because of its low toxicity, and the use of this isocyanate will accordingly be discussed in more detail. Numerous examples of the use of diisocyanate chain extension of aliphatic polyesters can be found in the scientific publications and in the patent literature [52-54]. 

The copolymerization approach has successfully been applied for poly(ester-urethane)s by equipping the prepolymers with elastomeric properties by copolymerization. e-Ca-prolactone-lactic acid copolymers have been reported to result in a significant increase in the strain and the flexibility [62]. Table 3.2 shows the changes in the material properties that have been achieved by varying the prepolymer composition [50, 62]. 

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