Crystallization confined

Strongly segregated systems, Todt > Tc < Tg with hard confinement. A strictly confined crystallization within MDs has been observed for strongly segregated diblock copolymers with a glassy amorphous block [29-42]. 

Ueda et al. [26] recently investigated a flow-oriented PE-fr-aPP diblock copolymer with Mw = 113 000 (Mn/Mw = 1.1) and a PE volume fraction of 0.48. This diblock copolymer is in the strong segregation regime (i.e., estimated xN = 10.5 and Todt = 290 °C) and has a lamellar morphology in the melt. They found a breakout phenomenon with the formation of spherulites in an intermediate crystallization temperature range 95 < Tc < 101 °C. At crystallization temperatures above 101 °C or below 95 °C spherulites were not formed and the crystallization was confined within the lamellar MD. Ueda et al. report that lamellar MD and spherulites do not co-exist when the material crystallizes from the melt which is separated in lamellar MDs. In other words, in this particular case, breakout or confined crystallization within lamellar MDs depends on the crystallization conditions. 

Several of the ABC triblock copolymers with two crystallizable blocks that have been studied include PE as one of the crystallizable components. The PE block can be found either at the end (PE-fo-PS-b-PCL [94], PE-fr-PEP-fo-PEO [101,119]) or at the center (PS-fr-PE-fr-PCL [98]). When the PE block is located at the center of the copolymer, as is the case in PS-fo-PE-fr-PCL triblock copolymers [94], there are higher constraints on the PE block owing to the absence of free ends. If the PE block is a minor component, confined crystallization with possible homogeneous nucleation is usually encountered. It may be possible that when the PE block does not have free ends, it may be... 

Batte, H.D., and Marangoni, A.G. (2005). Fractal growth of milk fat crystals is unaffected by microstructural confinement. Crystal Growth Des. 5, 1703-1705. 

C. Alvarez, A. Nogales, M. C. Garcia-Gutierrez, A. Sanz, Z. Denchev, S. S. Funari, M. Bruix, and T. A. Ezquerra. Confined crystallization in phase-separated poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6-dicarbox-ilate) blends. Eur. Phys. J. E, 18(4) 459-465, December 2005. 

Confined Crystallization in Microphcise-separated Poly (sty rene—block—octadecyImethacrylate)... 

Recently (2010), Hood et al. [227] reported research on a series of PUs, with high HS content. They were synthesized with the aliphatic diisocyanate HDI, and chain extended with EDO. The SS macrodiol poly(ethyleneglycol) (PEG) was chosen because it has low transition temperatures and desirable mechanical properties. A variety of molecular weights was chosen, in order to provide a wide temperature window to conduct confined crystallization studies. 

Pig. 8. Model for confined crystallization in a lamellar phase formed by a polyethylene-6-poly(vinylcyclohexane) diblock (159). 

Giusca CE, Stolojan V, Sloan J, Borrnert F, Shiozawa H, Sader K, Rummeli MH, Buchner B, Silva SRP. Confined crystals of the smallest phase-change material. Nano Lett 2013 13 4020-7. 

Because is less convex (positive) than, the compressive strength is negative, but it creates a tensile stress in the hoop direction around the pore. This tensile stress is the destructive "crystallization pressure" A high equilibrium aystallization pressure requires a confined crystal in a pore of any geometry with a very small pore entrance Therefore, the stones with a bimodal pore size distribution are extremely susceptible to salt attack Ii7-i9]... 

In a more fundamental vein, Zhang et al. [157] studied the confined crystallization behavior of PLA/acetylated BC nanocomposites prepared by compression molding. The results indicated that acetylated BC favored the crystallization of PLA at higher temperatures. In a similar mode, Quero et al. [158] investigated the micromechanical properties of laminated BC/PLA nanocomposites by Raman spectroscopy as a mean to understand the fundamental stress-transfer processes in these nanocomposites and as a tool to select appropriate processing and volume fraction of the fibers. Results showed that Young s modulus and stress at failure of PLA films were foimd to increase by 100 and 315%, respectively, for 18% volume fraction of BC and BC membranes cultured for 3 days exhibited enhanced interaction with PLA because of their higher total surface area. 

New physical, chemical or biological properties are caused by size scaling. Smaller particle size determines larger interfacial area, an increased number of molecules on the particle interfaces, quantum electromagnetic interactions, increased surface tension, and size confinement effects (from electronic and optic to confined crystallization and flow structures). The wavelike properties of the electrons inside matter are affected by shape and volume variations on the nanometer scale. Quantum... 

---