Influence of ionic groups on the crystallization and melting behavior of segmented polyurethane ionomers

Abstract

ABSTRACT:The isothermal crystallization kinetics and melting behavior of the soft segment in polyurethane (PU) ionomer/nonionomer based on PCL-4000 (poly(-caprolactone)) were investigated using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). In general, the presence of ionic groups in PU ionomers can promote the formation of a more stable crystalline structure and lower the equilibrium melting temperature of the crystallizable phase. Comparison between the crystallization characteristics of PU nonionomers and ionomers suggests that the Coulombic Forces between ionic groups within hard segment can increase the crystallization rate and decrease the crystal size of soft segment when the total molecular weight (M w ) of PU ionomer is higher than ϳ71,000. On the other hand, the opposite effect of ionic groups on the crystallization rate is observed in PU ionomers with M w below ϳ20,000. The DSC thermograms illustrate that the ionic groups can significantly enhance the microphase separation in PU ionomers with higher M w values. By the control and manipulation of crystallization and microstructure formation in PU ionomer, it is possible to achieve shape memory PUs with superior physical property.

Synthesis and antibacterial characterization of waterborne polyurethanes with gemini quaternary ammonium salt

“…Nevertheless, T g, soft of these GWPU samples are much lower compared with those of normal PTMG-based polyurethanes (around -45°C) [32], and these T g, soft have only tiny changes that increase firstly and then reduce with the increase in GQAS contents in GWPU (Table 1). This is due to a strong polarity difference between soft segment and hard segment containing polar lysine and GQAS moieties, leading to high degree of microphase separation in these GWPU matrixes [26,35]. As a result, the amount of EG12 and lysine introduced in hard segments has no significant effect on aggregation state of hard and soft segments in GWPU samples.…”

“…This interesting phenomenon will probably be helpful in achieving high contents of GQAS on these polyurethane surfaces [32,33], and these surface structures are characterized as ongoing work in our group. In addition, the exothermic peak observed at around 2°C and endothermic peak at 28°C in the curve of GWPU100 are attributed to reorganized crystallization of soft segment chains and melting temperature (T m ) of crystallized soft segment chains [36], which might be attributed to the lower molecular weight and enhanced polarity difference between hard and soft segment domains in GWPU100 [35].…”

Shape Memory Systems with Biodegradable Polyesters

“…So, efforts were dedicated to modify both soft and hard phases in order to improve the SM performance. The ways followed cover the use of other polyester diols than PCL (for example PLA-based ones [53][54]), additional crosslinking via functional POSS [55], incorporation of nanofillers [56][57], creation of ionomers [58], and blending [59][60], as well. …”

Synthesis and Properties of Shape Memory Poly(γ-Benzyl-l-Glutamate)-b-Poly(Propylene Glycol)-b-Poly(γ-Benzyl-l-Glutamate)

“…SMPs have an ability to change their shapes from temporary to original upon external stimuli, such as heat, light, and pH [4][5][6][7]. Among them, thermo-triggered SMPs are the most widely studied, and a number of thermally-actuated SMPs have been reported, such as polyurethanes, polyesters, polyacrylates, polynorbornene, and polyimide [8][9][10][11][12][13][14]. Typical thermo-responsive SMPs could be described as a netpoint-switch model as reported in our previous work [15], where the netpoints could be of physically or chemically cross-linking, determining permanent shapes, and the switches refer to amorphous or crystallization soft phase responsible for temporary shapes.…”