ISOMERISM: IS THERE MISCONCEPTION?

Nine articles have been analyzed containing research results on misconceptions about isomerism. Analysis was conducted to examine the potential to causes emergence of the misconception. The analysis result are expected to be useful for teachers in learning for the same concepts. At least the teacher can avoid misconceptions that have happened before and innovate to find the right learning strategy. Isomerism can be categorized as a defined concept so that students are expected to be able to use rules for the purpose of classifying objects or events. The analysis showed 31 misconceptions experienced by grade 11 students to prospective chemistry teachers on isomerism concept. Thirty-one misconceptions are classified into three groups based on students' abilities needed to understand the concept of isomerism. The three groups are: (1) understanding the definition and application of rules; (2) spatial understanding; and (3) microscopic understanding. At this time only eleven misunderstandings were discussed, namely misunderstandings whose causes belong to the group (1). As an indicator caused misconception is inability of the sample to classify objects/events based on the attributes or characters indicated by the object/event. To teach a defined concept, it is recommended to use a strategy that contains detailed explanatory definitions and rules, examples and non-examples, and the elaboration process. In order to increase student reasoning, it is recommended to use a isomerism concept logic scheme

Synthesis and Characterization of Speciality Polyurethane Elastomers

Dyed and un-dyed polyurethane elastomers have been synthesized via the prepolymer method and analyzed by using different analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, Proton nuclear magnetic resonance ( 1 H-NMR) and Carbon-13 nuclear magnetic resonance ( 13 C-NMR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning colorimetery (DSC) and thermogravimetric and differential thermal analysis (TG/DTA), tensile testing, contact angle measurement, water absorption percentage (%), density and hardness. FTIR and NMR techniques were used to confirm the chemical structure of the synthesized PUEs. While XRD was executed to determine the extent of crystallanity as a function of chain extenders, diisocyanates and for the dye (Disperse Red 5/1,4- butanediol) as chain extender. Which also have shown that the dye molecule becomes the part of the polymeric chain of the PUEs. Scanning electron microscopy was employed to analyze the surface morphology of PUEs with variation of chain extenders, diisocyantes and dye content. SEM images of PUEs have shown that hard segments are completely dispersed in the soft segment matrix. Other methods like contact angle measurement and water absorption percentage (%) were also used to determine the surface properties. The results have shown that the samples of PUEs based on HTPB were hydrophobic and this nature was increased as the chain extender length was increased. The same trend was observed in the variation of aromatic to aliphatic diisocyanates as well as the content of DR5 dye was increased. Thermal analysis was performed to analyze the thermal behavior of the PUEs by using TG/DTA and DSC which show that all the PUEs were stable up to 215 o C and all the samples were degraded to constant mass at 470 o C. Mechanical properties of the PUEs were studied by tensile testing, it is revealed that chain extender length and diisocyantes affect the mechanical properties while dyed polyurethane had represented the inverse mechanical behaviour with respect to un- dyed PUEs. The present study gave us reliable results for dyed and un-dyed PUEs and it was found that the dye had been incorporated in the polymeric chains and the effect was significant on surface morphology, thermal and mechanical properties such as tensile strength, modulus and elongation at break.