Diazo-Based Copolymers for the Wet Strength Improvement of Paper Based on Thermally Induced CH-Insertion Cross-Linking

Abstract

We present an alternative to commonly used, but from an environmental point of view, problematic wet strength agents, which are usually added to paper to prevent a loss of mechanical stability and finally disintegrate when they get into contact with water. To this end, diazoester-containing copolymers are generated, which are coated onto paper and by heating to 110–160 °C for short periods of time become activated and form carbene intermediates, which undergo a CH-insertion cross-linking reaction. The process leads to a simultaneous cross-linking of the polymer and its attachment to the cellulose substrate. The immobilization process of copolymers consisting of a hydrophilic matrix based on N,N-dimethylacrylamide and a diazoester-based comonomer to a cellulose model surface and to laboratory-engineered, fibrous paper substrates is investigated as a function of time, temperature, and cross-linker composition. The distribution of the polymer in the fiber network is studied using confocal fluorescence microscopy. Finally, the tensile properties of modified wet and dry eucalyptus sulfate papers are measured to demonstrate the strong effect of the thermally cross-linked copolymers on the wet strength of paper substrates. Initial experiments show that the tensile indices of the modified and wetted paper samples are up to 50 times higher compared to the values measured for unmodified samples. When dry and wet papers coated with the above-described wetting agents are compared, relative wet strengths of over 30% are observed.

Thermal Structuring of Surface‐Attached Polymer Networks by C,H Insertion Reactions

“…Similarly, the synthesis of terpolymers containing a small amount of the xanthene fluorescence dye rhodamine B was performed. [ 33 ] Rhodamine B methacrylamide (RhBMA), obtained from rhodamine B by reaction with ethylenediamine and methacrylic acid chloride, was used for this purpose. [ 34 ]…”

“…Similarly, the synthesis of terpolymers containing a small amount of the xanthene fluorescence dye rhodamine B was performed. [33] Rhodamine B methacrylamide (RhBMA), obtained from rhodamine B by reaction with ethylenediamine and methacrylic acid chloride, was used for this purpose. [34] The polymerization was carried out through free radical solution polymerization at 30 °C in DMF under vacuum using the initiator 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) for 17 h. The azo initiator V-70 with a half-life of 10 h at 30 °C allows for mild conditions during polymerization, thus preventing premature network formation caused by the decomposition of the diazo group of PEDAz during polymerization.…”

Transparent and Superhydrophilic Flexible Protein Films with Antifogging and Self-Cleaning Attributes

“…To further explore the role of wetting on the mechanical properties of LGAT films, the films were immersed in water for 60 s, followed by blotting with a tissue paper in order to remove the excess water. Relative wet strengths were evaluated following the technique described by Schölch et al The following equations were used to assess the relative wet strengths where, F max is the maximum force at break (Newton), b is the width of the films (mm), and the grammage of the films (g/m 2 ).…”

“…To further explore the role of wetting on the mechanical properties of LGAT films, the films were immersed in water for 60 s, followed by blotting with a tissue paper in order to remove the excess water. Relative wet strengths were evaluated following the technique described by Schölch et al The following equations were used to assess the relative wet strengths relative .25em wet .25em strength = wet .25em tensile .25em index dry .25em tensile .25em index × 100 wet / dry .25em tensile .25em index = F max b × grammage × 1000 where, F max is the maximum force at break (Newton), b is the width of the films (mm), and the grammage of the films (g/m 2 ).…”

Controlling Fluorescent Readout in Paper-based Analytical Devices

“…In order to reduce this, paper samples were dipcoated with a hydrophilic copolymer containing benzophenone units, p(DMAA-1%-MABP), which had been incorporated into the polymers through a standard free radical copolymerization procedure, as already discussed in previous work. 40 The surface modification significantly reduces the nonspecific protein adsorption and allows molecules to reach the detection line, thanks to an entropic shielding effect. 41−44 p(DMAA-1%-MABP) coatings also increase the wet strength properties, an important aspect for analytical device manufacturing.…”