Saraswathy Manju, Stansbury Jeffrey W, Nair Devatha P
Department of Craniofacial Biology University of Colorado-School of Dental Medicine, Aurora, CO 80045, USA.
Department of Craniofacial Biology University of Colorado-School of Dental Medicine, Aurora, CO 80045, USA; Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
J Mech Behav Biomed Mater. 2017 Oct;74:296-303. doi: 10.1016/j.jmbbm.2017.04.023. Epub 2017 Apr 27.
Significant efforts have been expended to mitigate plasticizer migration from crosslinked methacrylic and poly(vinyl chloride) polymer networks by synthesizing reactive plasticizers that can blend homogenously within the networks to reduce polymer property change, acute toxicity and downstream environmental effects of plasticizer migration with limited and varying amount of success. We hypothesized that appropriate thiol-functionalized nanogels synthesized using the same monomers as the parent network to generate highly compact, crosslinked structures will form thermally stable, homogenous networks and perform as optimal reactive plasticizers. Nanogels were synthesized via a thiol-Michael addition solution polymerization and incorporated at different mass ratios within a polyethylene glycol 400 urethane dimethacrylic monomer to form photo-crosslinked networks. While maintaining the inherent hydrolytic stability, thermal stability and biocompatibility of the parent matrix at ~99% acrylic group conversion, the PEG400 urethane dimethacrylic -nanogel networks retained optical clarity with >90% visible light transmission at 20wt% nanogel concentration within the matrix. The addition of the nanogels also enhanced the elongation of the parent matrix by up to 320%, while a 37°C reduction in glass transition temperature (∆T) and ≥50% reduction in modulus was observed. A 52% reduction in the shrinkage stress of the material was also noted. The results indicate that the application of thiol-functionalized nanogels as plasticizers to alter the bulk properties of the parent matrix while mitigating plasticizer migration by covalently crosslinking the nanogels within the polymer matrix provides a simple yet efficient technique to generate network-specific plasticizers with the ability to alter targeted properties within polymers.
人们已经付出了巨大努力，通过合成可在聚合物网络中均匀混合的反应性增塑剂，来减轻交联甲基丙烯酸和聚氯乙烯聚合物网络中的增塑剂迁移，以减少聚合物性能变化、急性毒性以及增塑剂迁移对下游环境的影响，不过取得的成功有限且效果各异。我们推测，使用与母体网络相同的单体合成的适当的硫醇官能化纳米凝胶，将形成高度致密的交联结构，从而形成热稳定的均匀网络，并作为最佳的反应性增塑剂发挥作用。纳米凝胶通过硫醇-迈克尔加成溶液聚合反应合成，并以不同质量比掺入聚乙二醇400聚氨酯二甲基丙烯酸单体中，以形成光交联网络。在母体基质的丙烯酸基团转化率约为99%时，聚乙二醇400聚氨酯二甲基丙烯酸-纳米凝胶网络在保持其固有的水解稳定性、热稳定性和生物相容性的同时，在基质中纳米凝胶浓度为20wt%时，仍保持光学透明度，可见光透过率>90%。纳米凝胶的加入还使母体基质的伸长率提高了320%，同时观察到玻璃化转变温度（∆T）降低了37°C，模量降低了≥50%。还注意到材料的收缩应力降低了52%。结果表明，将硫醇官能化纳米凝胶用作增塑剂，通过在聚合物基质中共价交联纳米凝胶来改变母体基质的整体性能，同时减轻增塑剂迁移，这提供了一种简单而有效的技术，可生成具有改变聚合物中目标性能能力的特定网络增塑剂。
