Initiator-tightened compositions
Disclosed herein are gel and plastic compositions comprising tightened layers of polymerized vinyl monomers, as well as methods of making the same, where the layers are tightened in having smaller pores. The tightened layers comprise tightened inner layers and exterior layers, and the compositions comprise polymer-attached (pendant) initiator or helper residues.
1. A hydrogel, the hydrogel comprising an exposed surface layer of polymerized vinyl monomers forming a vinyl polymer and an interior layer of polymerized vinyl monomers forming a vinyl polymer, the exposed surface layer having a lower porosity than the porosity of an interior layer;
wherein both the exposed surface layer and interior layer comprise one of the following: 1) a plurality of polymer-attached initiator residues, 2) a plurality of polymer-attached helper residues, or 3) a combination of polymer-attached initiator residues and polymer-attached helper residues, and
wherein the vinyl polymer of the exposed surface layer has a higher content of 1), 2) or 3) than the vinyl polymer of the interior layer and the porosity of the exposed surface layer allows retention of a particle of about 1 kDa.
2. The hydrogel of claim 1 , wherein the plurality of polymer-attached initiator residues comprises two different initiator residues.
3. The hydrogel of claim 1 , wherein the plurality of polymer-attached initiator residues comprises sulfate or hydroxy.
4. The hydrogel of claim 1 , wherein the plurality of polymer-attached helper residues comprises N,N,N′,N′-tetramethylethylenediamine lacking a hydrogen atom on a carbon atom.
5. The hydrogel of claim 1 , wherein the vinyl polymer of the interior layer or the exposed surface layer has a plurality of polymer-attached vinyl groups.
6. The hydrogel of claim 5 , wherein a ratio of polymer-attached initiator or helper residues to polymer-attached vinyl groups in at least one portion of the hydrogel is greater than 10.
7. The hydrogel of claim 6 , wherein a ratio of polymer-attached initiator or helper residues to polymer-attached vinyl groups in at least one portion of the hydrogel is greater than 100.
8. A hydrogel comprising polymerized vinyl monomers, the hydrogel comprising an interior layer of polymerized vinyl monomers, the interior layer having a lower porosity than the porosity of an exposed exterior layer, and the interior layer having a ratio of polymer-attached initiator or helper residues to polymer-attached vinyl groups which is greater than 10, wherein the porosity of the exposed exterior layer allows retention of a particle of about 1 kDa.