Effect of organic and inorganic ions on the lower critical solution transition and aggregation of PNIPAM

Soft Matter ◽  
2018 ◽  
Vol 14 (38) ◽  
pp. 7818-7828 ◽  
Author(s):  
Leonor Pérez-Fuentes ◽  
Delfi Bastos-González ◽  
Jordi Faraudo ◽  
Carlos Drummond
Keyword(s):  
Differential Scanning Calorimetry ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Inorganic Ions ◽  
Hofmeister Series ◽  
Scanning Calorimetry ◽  
Thermosensitive Polymer

We have studied the effect of different ions belonging to the extended Hofmeister series on the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAM), by combining Differential Scanning Calorimetry (DSC) and Dynamic Light Scattering (DLS).

Phase transitions of liposomes: When light meets heat

2021 ◽  
Author(s):  
C S Velez-Saboyá ◽  
J R Guzmán-Sepúlveda ◽  
Jesus Carlos Ruiz-Suárez
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Membrane Thickness ◽  
Scanning Calorimetry ◽  
Contraction Process ◽  
Exothermic Process ◽  
Gel Phase ◽  
Derivatives Of

Abstract Phase transitions of liposomes are normally studied by differential scanning calorimetry (DSC). A suspension of liposomes is subjected to an increase (decrease) of temperature and when heat is absorbed (released), the liposomes transit from a gel (liquid) to a liquid (gel) phase. This endothermic (exothermic) process takes place at a temperature called the melting temperature Tm, which is distinctive of the type of lipids forming the vesicles. The vesicles, though, also modify their size in the transition. Indeed, the thickness of the membranes decreases (increases) because carbon tails misalign (align). Concomitant with the modifications in the membrane thickness, the diameter (D) of the liposomes changes too. Therefore, when they are inspected by light, the scattered signal carries information from such dilatation (contraction) process. We performed careful experiments using dynamic light scattering (DLS) as a function of temperature to detect the size changes of different liposomes. Gaussian fits of the derivatives of the D vs T curves coincide within 1% with thermograms, which hints to the possibility of performing thermodynamic studies of lipid systems employing light.

Photophysical properties of microencapsulated phthalocyanines

2010 ◽  
Vol 14 (03) ◽  
pp. 278-283 ◽  
Author(s):  
Virginia E. Diz ◽  
Gabriela A. Gauna ◽  
Cristian A. Strassert ◽  
Josefina Awruch ◽  
Lelia E. Dicelio
Keyword(s):  
Differential Scanning Calorimetry ◽  
Light Scattering ◽  
Quantum Yield ◽  
Fluorescence Quantum Yield ◽  
Photophysical Properties ◽  
Oxygen Production ◽  
Electronic Microscopy ◽  
Scanning Calorimetry ◽  
Singlet Molecular Oxygen ◽  
Photophysical Parameters

Lipophilic substituted zinc(II) phthalocyanines: 2,3,9,10,16,17,23,24-octakis[(N,N-dimethylaminoethylsulfanyl)]phthalocyaninatozinc(II) (S1) and tetrakis(N,N-dibutylaminoethoxy)phthalocyaninatozinc(II) (3) were incorporated into soybean L-α-phosphatidylcholine (SPC) liposomes of 100 nm diameter. Liposomes were characterized by static light scattering (SLS), transmission electronic microscopy (TEM), and differential scanning calorimetry. The fluorescence quantum yield and singlet molecular oxygen production of 3 are Φ F = 0.15 and ΦΔ = 0.24, respectively, whereas the same photophysical parameters for S1 are Φ F = 0.13 and ΦΔ = 0.51. Higher values of Φ F and ΦΔ are obtained in organic solvent for both dyes. Synthesis of compound 3 has also been reported.

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