ABSTRACT:Crosslinked polyurethanes (CPUs) were synthesized by reaction of (ethylene oxide-propyleneoxideethyleneoxide) (EO-PO-EO) triblock copolymer with diisocyanate and a low molecular weight triol as a crosslinking agent. The short diol was used as a chain extender. The effect of some factors such as the nature and content of PAOs, short diol chain extender and triol crosslinking agent on the phase separation of CPUs was studied by infrared spectroscopy (IR) and differential scanning calorimetry (DSC). The presence of amine group-containing compounds favors the phase separation of CPUs. The swelling behavior of CPUs in the different media such as aqueous solution and ethanol (EtOH)-water mixture has been investigated. The CPUs show the negatively thermosensitive swelling behavior. The collapsing swelling process in response to the change in environmental temperature was observed in CPUs prepared from EO-PO-EO triblock copolymer having a commercial code L92. In a EtOH-water mixture, CPUs reached the maximum swelling degree at the ratio EtOH/water 80/20 at the whole range of the environmental temperature due to the coupling effect.

Vocabulary plays an important role in English teaching and learning because it can stimulate students’ participation and help students improve their skills such as listening, speaking, reading and writing. This study was conducted to determine how vocabulary is presented and what factors affect students' motivation in learning vocabulary lesson and thus, suggest some ways of improving the effectiveness of vocabulary teaching and learning at the University of Technology (TNU), Thai Nguyen, Viet Nam. The data was collected by using two research instruments, including questionnaires and interviews. The results showed that both lecturers and students found a lot of benefits from using techniques in presenting vocabulary such as visual aids and verbal means. However, there were some difficulties teaching and learning new words at TNU. The research is also believed to be a reliable source of reference for teachers to enhance the effectiveness of using techniques of presenting vocabulary. Hopefully, it will be the springboard for many further studies in the future in the same research field.