Dataset on hydrophobicity indices and differential scanning calorimetry thermograms for poly(HEMA)-based hydrogels

Hydrophobicity indices for poly(HEMA)-based hydrogels: HEMA, AEMA, and DMAEMA calculated from two different methods: 1) Partition coefficients, and 2) Kyte-Doolittle scale are depicted. Thermograms from differential scanning calorimetry of poly(HEMA)-based hydrogels containing AEMA, DMAEMA, and a mixture of AEMA and DMAEMA are included to represent the glass transition temperature (Tg) values of the hydrogels. More information on the methodology to calculate the hydrophobicity indices using the aforementioned methods and the procedure for using a differential scanning calorimeter and analysis of a thermogram is described. Details of how the changes in the feed composition of poly(HEMA)-based hydrogels was made is provided in the research article ‘MOLECULAR ENGINEERING OF POLY(HEMA-co-PEGMA)-BASED HYDROGELS: ROLE OF MINOR AEMA AND DMAEMA INCLUSION’ (Bhat et al., 2019).[1].


Data
Hydrophobicity indices and differential scanning calorimetry thermograms are described for HEMA, AEMA, and DMAEMA poly(HEMA)-based hydrogels. Hydrophobicity indices are established by two methods. The first method mentions the hydrophobicity indices for the monomers based on the partition coefficients of monomers [2] derived from their functional group contributions. Table 1 lists the hydrophobicity indices using the first method. The second method determines the hydrophobicity indices for the monomers based on comparisons of their functional groups with the Kyte-Doolittle scale [3] for amino acids. Table 2 shows the hydrophobicity indices using the second method. Figs. 1e4. Depict the differential scanning calorimetry thermograms for poly(HEMA)-based hydrogel polymers synthesized to contain 4 mol% HEMA, 4 mol% AEMA, 4 mol% DMAEMA, and 2 mol% AEMA plus 2 mol% DMAEMA. Table 3 shows the glass transition temperature, T g , for all four poly(HEMA)based hydrogel formulations.

Data format
Analyzed Experimental factors 4 mol% HEMA, 4 mol% AEMA, 4 mol% DMAEMA, and 2 mol% AEMA þ 2 mol% DMAEMA were analyzed using differential scanning calorimetry (DSC) with an associated software. To determine the glass transition temperature (T g ) of the hydrogels, samples were first dehydrated.

Experimental features
To determine the glass transition temperature (T g ) of the hydrogels, samples were first dehydrated then placed and sealed into hermetic pans (Tzero hermetic lid, 901684.901; Tzero pan, 901683.901), equilibrated at -20 C and heated to 200 C at 10 C/min for two cycles. The first cycle was performed in order to erase the thermal history of the hydrogels, and the second cycle was performed in order to determine the inherent thermal properties of the hydrogels. The  Table 4 were handled in a UV-free laboratory with UV filtering sleeves (TG-T8TG-UV, Lightbulbsurplus.com) placed over the fluorescent light bulbs. Four unique hydrogel pre-polymer formulations were prepared that varied in composition and were synthesized from HEMA, AEMA and DMAEMA by varying 4 mol% (nominally) of the responsive and cationogenic constituent. Thus, all hydrogels comprised 80 mol% HEMA. The formulation referenced as 4 mol% HEMA contained an additional 4 mol% HEMA to a total of 84 mol%  HEMA and served as a reference formulation. Other hydrogels were formulated by replacing the 4 mol% HEMA with 4 mol% AEMA, 4 mol% DMAEMA, or a mixture of comprising 2 mol% AEMA and 2 mol% DMAEMA. To improve component solubility, a mixed solvent comprising 1:1 (v/v) ratio of ethylene glycol and DI water was added to the mixture such that it comprised 20 vol% of the formulation. Finally, the mixture was ultrasonicated for 5 min and sparged with nitrogen gas to remove dissolved oxygen prior to casting and crosslinking [1].
To prepare hydrogel samples for characterization and testing, the hydrogel formulations were cast inside press-to-seal silicone isolator chambers (JTR12R-2.0, Grace Biolabs, Bend, OR) comprising 12 each of 4.5 mm diameter x 1.6 mm depth that were placed between two hydrophobically prepared glass slides. Prior to casting, both sides of the glass slides were thoroughly degreased with acetone, UV cleaned for 10 min (UV-ozone Cleaner, Boekel Industries Inc., Feasterville, PA) and sonicated in  isopropyl alcohol to further remove contaminants. The slides were then plasma cleaned (Plasma cleaner/sterilizer PDC-32 G, Harrick Plasma, Ithaca. NY) to activate eOH groups and immediately incubated in a freshly prepared solution of 0.1% octadecyltrichlorosilane (OTS) in toluene for 45 minutes. The glass slides were then sonicated in isopropyl alcohol for 5 minutes and the silanol condensation with eOH groups of the glass allowed to proceed in an oven by sequentially heating to 40, 110, and 40 C for 20 minutes at each temperature. Once cooled to RT the isolator was pressed to one glass slide and each chamber filled with the hydrogel cocktail. A second glass slide was then gently lowered onto the chambers. Hydrogels were UV crosslinked for 5 min (CX-2000, UVP, Upland, CA). Upon completion of cross-linking, the polymerized  Table 3 Glass transition temperature, T g , for all four poly(HEMA)-based hydrogel formulations containing 4 mol% HEMA, 4 mol% AEMA, 4 mol% DMAEMA, and 2 mol% AEMA þ 2 mol% DMAEMA (n ¼ 3, mean ± 95% C.I.) [1].
As monomers HEMA, AEMA and DMAEMA differ only with respect to their functional groups OH, NH 2 , and N(CH 3 ) 3 respectively, it is assumed that only these functional groups contribute to the partition coefficients.
For CH 3 [2]. For CH 3 OH and CH 3 NH 2 the log P values are negative indicating hydrophilicity. For N(CH 3 ) 3 , log P is 0.16 (positive), indicating hydrophobicity. These values serve to provide a relative ranking of the monomer along a continuum from highly hydrophilic to hydrophobic. b) Evaluating the hydrophobicity indices of the monomers using Kyte-Doolittle scale (for amino acids) [3].
Kyte-Doolittle scale [3] lists the hydrophobicity indices of amino acids. We allocated these hydrophobicity indices to our monomers based on their functional group similarity with the R-groups of amino acids.

Differential scanning calorimetry (DSC) thermograms
To determine the glass transition temperature (T g ) of the hydrogels, samples were first dehydrated then placed and sealed into hermetic pans (Tzero hermetic lid, 901684.901; Tzero pan, 901683.901), equilibrated at À20 C and heated to 200 C at 10 C/min for two cycles. The first cycle was performed in order to erase the thermal history of the hydrogels, and the second cycle was performed in order to determine the inherent thermal properties of the hydrogels. The T g was determined by extrapolation of thermal trace data using TA Universal Analysis software.