Fisher John P, Timmer Mark D, Holland Theresa A, Dean David, Engel Paul S, Mikos Antonios G
Department of Bioengineering, Rice University, PO Box 1892, MS 142, Houston, Texas 77251-1892, USA.
Biomacromolecules. 2003 Sep-Oct;4(5):1327-34. doi: 10.1021/bm030028d.
In this work, we investigated the mechanism involved in the photoinitiated cross-linking of the polyester poly(propylene fumarate) (PPF) using the initiator bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO). It was hypothesized that BAPO has the ability to cross-link PPF into solid polymer networks, without the use of a cross-linking monomer, because two pairs of radicals, both involving a fast adding phosphinoyl radical, were formed upon UV irradiation of BAPO. Spectroscopic investigation first confirmed the addition of BAPO derived radicals to the PPF olefin. Investigations of fumarate conversion and bulk network properties were then undertaken, using the BAPO initiator and a monoacylphosphine oxide (MAPO) initiator which contains a single photolabile bond. Results show that a single BAPO phosphinoyl radical was primarily responsible for the formation of a highly cross-linked PPF network and the additional radical pair which may be formed does not dramatically alter fumarate conversion or bulk network properties. From these results, the network structure of BAPO initiated, photo-cross-linked PPF may be deduced. Finally, this study demonstrates a method for inferring cross-linked network structures by contrasting properties of bulk materials formed from similar cross-linking initiators.
在这项工作中，我们研究了使用引发剂双（2,4,6-三甲基苯甲酰基）苯基氧化膦（BAPO）对聚富马酸丙二醇酯（PPF）进行光引发交联的机制。据推测，BAPO有能力在不使用交联单体的情况下将PPF交联成固体聚合物网络，因为在BAPO的紫外线照射下会形成两对自由基，这两对自由基都涉及一个快速加成的膦酰基自由基。光谱研究首先证实了BAPO衍生的自由基加成到PPF烯烃上。然后，使用BAPO引发剂和含有单个光不稳定键的单酰基氧化膦（MAPO）引发剂，对富马酸酯转化率和本体网络性能进行了研究。结果表明，单个BAPO膦酰基自由基主要负责形成高度交联的PPF网络，可能形成的额外自由基对不会显著改变富马酸酯转化率或本体网络性能。根据这些结果，可以推断出BAPO引发的光交联PPF的网络结构。最后，本研究展示了一种通过对比由相似交联引发剂形成的本体材料的性能来推断交联网络结构的方法。
