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A reliable thermal interface material (TIM) typically has a low storage modulus ( \textG^\prime ) and a tan( $\delta$ ) less than one; these mechanical properties are crucial for minimizing contact resistance ( \mathbf {R}_{\mathbf {c}} ). This paper demonstrates the correlation between storage modulus ( \textG^\prime ) and the crosslink density of silicone gels. Formulations span between 0.30 and 1.00 hydride to vinyl (H:Vi) ratios for the vinyl terminated and hydride pendent polymers used in the gel. These gels are tailored for TIM applications by adding highly conductive particles to improve thermal conductivity. During this study, when 80 wt% conductive filler was added to gels with a 0.6 H:Vi ratio, the \textG^\prime increased by 6025%. In order to minimize \textG^\prime , the crosslinker in the formulation was replaced with a chain extender. With this formula substitution, the modulus of the filled gel can be successfully lowered to the original value of the unfilled gel while maintaining the crucial properties of a reliable TIM. In effect, it is possible to independently optimize the thermal conductivity of a TIM while creating a compliant gel that maintains surface contact and minimizes contact resistance. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis, physicochemical properties and modifications of 2-hydroxyethyl methacrylate copolymers. It describes the new 2-hydroxyethyl methacrylate hydrogels in the form of microbeads of different degrees of crosslinking (2, 5, 8, 10, 15 and 20% mol). As crosslinking monomers bis[4(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-sulfide and ethylene glycol dimethacrylate were used. The new hydrogels were obtained by two alternative methods in a suspension copolymerisation procedure. The copolymers were modified with diethylenetriamine in an epoxide opening reaction. Thermal properties (differential scanning calorimetry, thermogravimetric analysis) and swelling characteristic in typical solvents of the obtained functional hydrogels were examined. The chemical structure of the copolymers before and after modification was confirmed by Fourier transform infrared spectroscopy and elemental analyses. Moreover, their sorptive properties in removal of Cu(II), Zn(II), Cd(II), and Pb(II) ions from aqueous solutions were also presented. The Langmuir and Freundlich isotherm models are used to describe the adsorption characteristics of the selected modified hydrogels.

Purpose: This work describes the characterization and evaluation of a tissue-mimicking thermochromic phantom (TMTCP) for direct visualization and quantitative determination of temperatures during radiofrequency ablation (RFA). Methods: TMTCP material was prepared using polyacrylamide gel and thermochromic ink that permanently changes color from white to magenta when heated. Color vs temperature calibration was generated in matlab by extracting RGB color values from digital photographs of phantom standards heated in a water bath at 25-75 °C. RGB and temperature values were plotted prior to curve fitting in mathematica using logistic functions of form f(t) = a + b/(1 + e (c(t-d))), where a, b, c, and d are coefficients and t denotes temperature. To quantify temperatures based on TMTCP color, phantom samples were heated to temperatures blinded to the investigators, and two methods were evaluated: (1) visual comparison of sample color to the calibration series and (2) in silico analysis using the inverse of the logistic functions to convert sample photograph RGB values to absolute temperatures. For evaluation of TMTCP performance with RFA, temperatures in phantom samples and in a bovine liver were measured radially from an RF electrode during heating using fiber-optic temperature probes. Heating and cooling rates as well as the area under the temperature vs time curves were compared. Finally, temperature isotherms were generated computationally based on color change in bisected phantoms following RFA and compared to temperature probe measurements. Results: TMTCP heating resulted in incremental, permanent color changes between 40 and 64 °C. Visual and computational temperature estimation methods were accurate to within 1.4 and 1.9 °C between 48 and 67 °C, respectively. Temperature estimates were most accurate between 52 and 62 °C, resulting in differences from actual temperatures of 0.6 and 1.6 °C for visual and computational methods, respectively. Temperature measurements during RFA using fiber-optic probes matched closely with maximum temperatures predicted by color changes in the TMTCP. Heating rate and cooling rate, as well as the area under the temperature vs time curve were similar for TMTCP and ex vivo liver. Conclusions: The TMTCP formulated for use with RFA can be used to provide quantitative temperature information in mild hyperthermic (40-45 °C), subablative (45-50 °C), and ablative (>50 °C) temperature ranges. Accurate visual or computational estimates of absolute temperatures and ablation zone geometry can be made with high spatial resolution based on TMTCP color. As such, the TMTCP can be used to assess RFA heating characteristics in a controlled, predictable environment. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis, physicochemical properties and modifications of 2-hydroxyethyl methacrylate copolymers. It describes the new 2-hydroxyethyl methacrylate hydrogels in the form of microbeads of different degrees of crosslinking (2, 5, 8, 10, 15 and 20% mol). As crosslinking monomers bis[4(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-sulfide and ethylene glycol dimethacrylate were used. The new hydrogels were obtained by two alternative methods in a suspension copolymerisation procedure. The copolymers were modified with diethylenetriamine in an epoxide opening reaction. Thermal properties (differential scanning calorimetry, thermogravimetric analysis) and swelling characteristic in typical solvents of the obtained functional hydrogels were examined. The chemical structure of the copolymers before and after modification was confirmed by Fourier transform infrared spectroscopy and elemental analyses. Moreover, their sorptive properties in removal of Cu(II), Zn(II), Cd(II), and Pb(II) ions from aqueous solutions were also presented. The Langmuir and Freundlich isotherm models are used to describe the adsorption characteristics of the selected modified hydrogels. [ABSTRACT FROM AUTHOR]