Abstract
The effect of the anchoring group on the detailed polymerization kinetics was investigated using monomethacryloxy-heptaisobutyl POSS (1M-POSS). This compound was copolymerized with lauryl methacrylate (LM) as the base monomer, at various molar ratios. The process was initiated photochemically. The polymerization kinetics were followed by photo-DSC and photorheology while the polymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). For comparison, a methacrylate containing the branched siloxy-silane group (TSM) was also studied. It was found that the modifiers with a bulky substituent have a dual effect on the termination process: (i) At low concentrations, they increase the molecular mobility by increasing the free volume fraction, which leads to an acceleration of the termination and slows the polymerization; while (ii) at higher concentrations, they retard molecular motions due to the “anchor effect” that suppresses the termination, leading to acceleration of the polymerization. The anchor effect can also be considered from a different point of view: The possibility of anchoring a monomer with a long substituent (LM) around the POSS cage, which can further enhance propagation. These conclusions were derived based on kinetic results, determination of polymerization rate coefficients, and copolymer analysis.
Highlights
In recent years, there has been growing interest in high-performance inorganic–organic hybrid polymer materials
The photopolymerization kinetics of the lauryl methacrylate (LM)/1M-polyhedral oligomeric silsesquioxanes (POSSs) and LM/TSM systems were followed at 40 ◦ C in a wide range of the comonomer ratios
Due to the fact that the effects of two different monomers with bulky substituents were compared, the concentrations of the formulation components were set in mole percent. 1M-POSS showed a limited solubility with LM
Summary
There has been growing interest in high-performance inorganic–organic hybrid polymer materials Both components (the inorganic modifier and the polymer matrix) can be linked together physically or by chemical links. POSSs are organic–inorganic hybrid compounds constituted by an inorganic silica cage described by the general formula Rn(SiO1.5 )n or Tn , where n is the number of repeat units (n = 8, 10, or 12, T is RSiO1.5 ) and R is H or an organic substituent. This results in the POSS molecule having a unique shape: the inorganic core is surrounded by an organic outer layer. The size of the POSS cage is ~1.5 nm [1]
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