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1

The interaction of poly(L-lactic acid) and the nucleating agent N,N'-bis(benzoyl) suberic acid dihydrazide

Cai Y.-H., Zhao L.-S.

Polimery

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2015

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T. 60, nr 11-12

693--699

EN

Since N,N'-bis(benzoyl) suberic acid dihydrazide [NA(S)] acts as a powerful nucleating agent for poly(L-lactic acid) (PLLA), it is necessary to study the nucleation mechanism of NA(S) in the crystallization of PLLA. The interaction between PLLA and NA(S) was investigated by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and temperature-dependent Raman spectroscopy. The results from FT-IR and temperature-dependent Raman spectroscopy showed that a hydrogen bond between the C=O of PLLA and the N-H of NA(S) was formed. The TGA also indicated the existence of an intense interaction between PLLA and NA(S), resulting in the potent nucleation ability of NA(S) for PLLA. Molecular dynamics simulations (MDS) were employed to simulate the interaction of PLLA on the NA(S) surface. The simulation results further confirmed the hydrogen bond between PLLA and NA(S). The MDS study also analyzed the interaction energy between PLLA and NA(S). The MDS results can be used to select the proper nucleating agents and design novel organic nucleating agents.

PL

Zbadano mechanizm zarodkowania przy użyciu N,N'-bis(benzoilo)dihydrazydu kwasu suberynowego [NA(S)] w procesie krystalizacji poli(kwasu L-mlekowego) (PLLA). Interakcje między cząsteczkami PLLA i NA(S) oceniano na podstawie spektroskopii w podczerwieni z transformacją Fouriera, analizy termograwimetrycznej oraz widm Ramana, rejestrowanych w różnej temperaturze. Stwierdzono, że pomiędzy tlenem z grupy C=O w łańcuchu PLLA a wodorem z grupy N-H obecnej w NA(S) tworzą się wiązania wodorowe. Analiza TGA wykazała, że ww. intensywne interakcje są wynikiem dużej zdolności NA(S) do zarodkowania krystalizacji PLLA. Do zbadania oddziaływań na powierzchni NA(S) zastosowano także symulacje metodą dynamiki molekularnej (MDS), które potwierdziły występowanie wiązań wodorowych PLLA/NA(S). Metodą MDS określono też energię interakcji (technika MDS może być wykorzystana przy wyborze środka zarodkującego odpowiedniego dla danego układu).

2

Real glass crystallization high resolution electron microscopy (HREM) study and classic nucleation theory concept

Stoch L.

Optica Applicata

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2005

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Vol. 35, nr 4

819-827

EN

Formation of crystal phases in glass and the kinetics of the crystal growth are commonly interpreted on the basis of classical nucleation theory (CNT), a thermodynamic description of the formation and growth of clusters of atoms (nuclei) of a new phase in heterogeneous system. The high resolution electron microscopy (HREM) has been used to recognize this clusters (nuclei) formation, their nature and structure. The atomic scale mechanism of the formation of the crystal phase structure within the disordered structure of glass near the temperature Tg was studied. HREM and other methods of the early stages of crystallization of the SiO2-Al2O3-MgO glass studies, with TiO2 as a crystallization activator, revealed that glass crystallization can be realized directly through rearrangement of the parent glass structure elements as disorder-order transformation. Its mechanism is similar to the solid solution decomposition or polymorphic transformation. However in the glass with ZrO2 admixture, crystallizing in a liquid state, the mechanism of crystal phase formation is different. Zirconia ZrO2 particles precipitate and cordierite crystals are growing on them. Validity of CNT for describing the near glass transformation temperature Tg crystallization and nano glass ceramics formation appears disputable. Alternative way of explaining this process is proposed.

3

Nanocrystalline glass-ceramics formation

Stoch L.

Optica Applicata

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2003

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Vol. 33, nr 1

115-123

EN

The atomic scale mechanism of the transition of the glass structure into the structure of a compound crystallizing in it has been studied. It has been demonstrated that near the glass transformation temperature Tg the crystallization by direct ordering of the amorphous glass structure through local displacements of its elements can take place. TiO2 nucleated crystallization of SiO2-Al2O3-MgO glass-ceramics is the example. Up to now, it has been thought that amorphous phase separation is an indispensable step in the glass-ceramization. Crystallization with the direct ordering mechanism creates the compounds whose chemical composition and structure are close to those of glass network or to the domains and clusters in it. The (Mg, Al)-titanate, and high quartz structure solid solutions appearence are here the example.