The Morphology And Enzymatic Degradation Of Poly(1,4-butylene Adipate) And Its Blends

Biodegradable polymer materials have good degradability in natural environment.They have great application prospects in maintaining ecological balance and biological diversity.Polymer blending can endow the materials high performance and functionalization.In polymer blending,the strong or weak interactions between different components directly affect the phase separation and morphology of the materials.And they play a key role in regulating the properties of the materials.In this work,biologic aliphatic poly(1,4-butylene adipate)(PBA)was used as research object.The films were prepared by blending the atactic poly(3-hydroxybutyrate)(aPHB)or polyhydroxystyrene(PVPh).PVPh and aPHB have different interactions with PBA.The effects of aPHB and PVPh on the morphology and biodegradability of PBA were explored.A small amount of(1%)polyvinyl butyral(PVB)was introduced as a diluent to study how the morphology and phase transition behavior effect the PBA.The form distribution of pure PBA ring spherulites is investigated.This research will provide a theoretical basis for the regulation of the condensed structure and biodegradation behavior of aliphatic polyester.This work mainly includes:1.The aPHB was firstly prepared by anionic polymerization.And the PB A/aPHB blends and PBA/PVPh blends were obtained by the method of solution blending.The calculations of interaction parameter was introduced to demonstrate that the PBA/aPHB blends and PBA/PVPh blends are thermodynamically miscible at the melting state.It was found that the critical temperatures of neat ?-PBA crystallization decrease from 28 ? for neat PBA to 26 ? and 24 ? for the PBA/aPHB and PBA/PVPh,respectively.Moreover,the ?-to-a phase transition can be accelerated by incorporation of PVPh and aPHB.The(3-to-a phase transition completes at 55 during heating process for neat PBA,while the temperatures for a complete(3-to-a transition of PBA in PBA/aPHB and PBA/PVPh are 50 ? and 45 ?,respectively.The restricted mobility of amorphous PBA imposed by aPHB and PVPh can slower down the degradation rate of PBA in the blends.The higher glass transition temperature and stronger intermolecular interaction between PVPh and PBA result in a slower degradation of PBA in the PBA/PVPh blend.Furthermore,in neat PBA,PBA/PVPh or PBA/aPHB,the degradation rate of ?-PBA crystals obtained via annealing is slower than that of ?-PBA prepared by isothermal crystallization,and even slower than that of ?-PBA.2.The effects of PVB on the crystallization kinetics and morphology of PBA were investigated.PBA/PVB is a thermodynamic compatible system.After adding 1 wt%PVB,the crystallization rate of PBA decreases as PVB is adsorbed on the PBA folding surface,and PVB can greatly reduce the nucleation rate of PBA at the high crystallization temperatures.At the same time,the addition of PVB resulted in the changing of the lamellae orientation of PBA,and the transformation from flat-on lamellae to the tilted edge-on lamellae was also observed.Due to the large phase separation of PBA/PVB blends,the thickness of PBA lamellae is not influenced,and the ?-to-? phase transition is not affected during the annealing process.3.The effect of different substrate on the ring-banded spherulites of PBA was investigated.Ring-banded spherulites can be grown on the silicon substrate with the film thickness of 120 nm while this phenomenon was not happened on the gold substrate.The polymorphic ring-banded spherulites of poly(butylene adipate)was studied,the two types of a and(3 crystals are all distributed in flat-on lamellae and edge-on lamellae.