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A series of homopolymer polypropylenes (PPs), within a weight-average molecular weight (M w ) range of 100-1600 kg/mol, were manufactured as dumbbell microspecimens. The effects of the molecular weight and shearinduced crystallization on the mechanical properties and morphology were studied to gain a better understanding of the structure-property relationship. The results showed that the crystallinity decreased from 50 to 41% and the lamellar thickness increased as M w increased. Tensile tests demonstrated that the stiffness and especially the tensile strength rose to extremely high values (Young's modulus ¼ 2400 N/mm 2 , stress at 30% strain ¼ 120 N/mm 2 ). Furthermore, the strain hardening effect was strongly affected by the lamellar thickness and highly oriented superstructures. Dynamic mechanical analysis demonstrated that the mobility of the molecular chains depended on M w and on the lamellar thickness. In addition, the viscoelastic properties of unannealed and annealed samples indicated further the existence of shishkebab structures caused by shear-induced crystallization during injection molding.

The aim of this work was to synthesize and investigate properties of a novel dimethacrylic monomer based on bioderived alicyclic diol—isosorbide. Its potential as a possible substitute of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (BISGMA), widely used in dental restorative materials and suspected for toxicity was assessed. The novel monomer was obtained in a three-step synthesis. First, isosorbide was etherified by a Williamson nucleophilic substitution and subsequently oxidized to isosorbide diglycidyl ether (ISDGE). A triphenyl phosphine catalyzed addition of methacrylic acid to ISDGE resulted in 2,5-bis(2-hydroxy-3-methacryloyloxypropoxy)- 1,4:3,6-dianhydro-sorbitol (ISDGMA). The monomer obtained was photopolymerized using camphorquinone/2-(dimethylamino)ethyl methacrylate initiating system. Next, compositions with triethylene glycol dimethacrylate (TEGDMA) were prepared and polymerized. Double bond conversion, polymerization shrinkage and water sorption of resulting polymers were determined. Selected mechanical (flexular strength and modulus, Brinell hardness) and thermomechanical (DMA analysis) properties were also investigated. BISGMA based materials were prepared as reference for comparison of particular properties.

Thermoplastic polyurethanes (TPUs) molded at 205, 215, and 235 ° C are monitored by SAXS and WAXS during straining. A non-affi ne nanostructure deformation and related evolution mechanisms are found. DSC and microscopy are applied. DSC shows two melting endotherms. The results indicate that melts kept below the second peak stay phase-separated. The orientation parameter f ( ε ) and d f /d ε from WAXS are related to chain orientation mechanisms (strain ε ). SAXS shows hard domains that are only correlated to a next neighbor ("sandwich"). Thick sandwiches lengthen more than thin ones. Thin-layer sandwiches feature a strain limit. Some are converted into thick-layer sandwiches. Two materials have tough hard domains. Material processed at 235 ° C is soft and contains weak hard domains that fail for ε > 0.75. of the material. Block copolymers synthesized by living polymerization are characterized by uniform block lengths. Processing of such compounds may result in lattice-like nanostructures or even in photonic crystals, in which the soft and the hard blocks reside completely in different domains. This is different with thermoplastic polyurethanes (TPU). Along with their chains a mixed sequence of soft segments and hard segments is found. Thus, even optimum process control only leads to domains of very diverse shape and size, the arrangement of which can rarely lead to lattice-like correlation. Moreover, soft domains may contain several hard segments. Consequently, the chemistry [ 1 ] and the processing conditions [2][3][4][5] defi ne the nanostructure that, in turn, determines the material's mechanical properties. The hard domains form physical cross-links and make the material behave rubber elastic. Because the hard domains are permanent only to a fi rst approximation, the stressstrain behavior of TPUs is subject to "strong hysteresis, time dependence and cyclic softening". [ 6 ] Thus maturing or aging may become a problem, if longer time elapses between investigations with different methods, because in this case the results may not be combined.

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