Degree of exfoliation

The block length must be controlled and must not be too long. High degrees of exfoliation are claimed using this approach. 

GA better than JS equal treatment effect but lesser degree of exfoliation in GA [5]... 

Advantages SA safety and efficacy in darker phototypes (Fitzpatrick V-VI) [4] Possible association with other substances such as TCA-g and PA to improve their absorption [1] Easier to manage than GA in terms of uniformity of application [1] SA and PA better than GA and JS in terms of risk of side effects and patient discomfort during treatment [1] GA better than JS equal treatment effect but lesser degree of exfoliation in GA [5]... 

The rheological behavior of these materials is still far from being fully understood but relationships between their rheology and the degree of exfoliation of the nanoparticles have been reported [73]. An increase in the steady shear flow viscosity with the clay content has been reported for most systems [62, 74], while in some cases, viscosity decreases with low clay loading [46, 75]. Another important characteristic of exfoliated nanocomposites is the loss of the complex viscosity Newtonian plateau in oscillatory shear flow [76-80]. Transient experiments have also been used to study the rheological response of polymer nanocomposites. The degree of exfoliation is associated with the amplitude of stress overshoots in start-up experiment [81]. Two main modes of relaxation have been observed in the stress relaxation (step shear) test, namely, a fast mode associated with the polymer matrix and a slow mode associated with the polymer-clay network [60]. The presence of a clay-polymer network has also been evidenced by Cole-Cole plots [82]. 

In the case of LDPE-clay nanocomposites, the mechanical behavior does not depend only on the degree of exfoliation or the clay content but also on the presence of substantial amounts of compatibilizer [93, 94]. Besides the chemical modification of the clay, it is then necessary to turn the polymer matrix more polar with the grafting of polar groups. Traditionally, MAH has been used as the polar group to induce compatibility due to the high reactivity of the anhydride group. 

The degree of exfoliation also depends on the melt flow rate of the polymer used. It was found that PP with high melt flow rate of 25 g/10 min results in the formation of well-exfoliated nanocomposites than with polymers possessing low melt flow rate [27]. The presence of PP-g-MA in CPN has the potential to create the heterogeneous nucleation effect, which alters the crystallization temperature [25,29]. 

The effects of interactions between functional PO chains and clay platelets, generating "confined" polymer fractions, onto the final performances of nanocomposites with particular reference to mechanical properties and thermal stability have been discussed in literature with wide reviews on the topic (Alexandre et al. 2002, Gopakumar et al. 2002, Sinha Ray and Okamoto 2003, Preston et al. 2004, Szazdi et al. 2006, Tjong 2006, Ciardelli et al. 2008). On the contrary, in absence of functionalities onto the backbone of POs, even if a certain degree of exfoliation can be reached by shearing forces, the lack of specific polar interactions negatively affects the general mechanical properties (Mittal 2007). 

Kim et al. conducted a comparative study on the effectiveness of treatment and side effects in the treatment of facial acne in 26 Korean patients by two agents, 70% glycolic add and Jessner s solution. Acne improved after three treatment sessions with both agents. However, a greato degree of exfoliation was observed with Jessner s solution [23]. 

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