•By nucleating agent and erasing thermo-history α and β crystal grow simultaneously.•The growth rates of α and β form were compared under the same Tc and Tm0.•The growth rate of β form is faster than that of α form for both sPS and BzsPS-2%.•BzsPS containing rigid comonomer is more favourable for α form comparing to sPS.•sPS with 5% benzoylation only form α form crystal below 225 °C.The crystallization behaviour of syndiotactic polystyrene (sPS) and benzoylated sPS (BzsPS) was investigated by POM, DSC and XRD. The results suggest β form of sPS has higher equilibrium melting temperature Tm0 and the fold surface free energy σe than α form. With increasing benzoylation degree the growth rates and Tm0 of two forms decrease, but their Tm0 decrement is very close; the σe of β form more increases than that of α form, the formation of α is more favourable. Upon loading trace amount of α nucleating agent PTBBNa in samples the growth rate of two forms can be strictly compared in the same melting and crystallization temperature condition, the results reveal that the growth rate of β form is faster than that of α form in sPS and BzsPS-2%. Using supercooling degree ΔT and σe two parameters has explained the formation competition mechanism of α and β forms.Loading trace amount of α heterogeneous fibrous nucleating agent PTBBNa in sPS and benzoylated sPS is a good way to investigate strictly the linear crystal growth rate of α and β forms under the same melt condition and the same crystallization temperature range. The results reveal that the trace amount of α nucleating agent PTBBNa loading in samples does not influence the growth rate of α and β forms and the growth rate of β form is faster than that of α form in both sPS and BzsPS-2% (with benzoylation degree of 2%) samples.

Microspheres with thermo-responsible surface were fabricated by PCL-b-PEO-b-PNIPAM triblock copolymers. Thermo-responsible morphological changes of PCL-b-PEO-b-PNIPAM microspheres immersed in aqueous solution at temperatures above the LCST (e.g. 37 °C) were observed from porous surface structure to compact surface layer. Enzymatic degradation and in vitro drug release results showed that the thermo-responsible surface layer greatly influenced the degradation of microspheres as well as the drug release behavior from microspheres. With the copolymerization of PNIPAM block into PCL-b-PEO copolymers, the drug release could be well regulated by changing temperatures and microspheres composition, which revealed the great potentials of microspheres with thermo-responsible surface for controlled drug release.

In the present work, a surfactant, the phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (abbreviated as NP-10P throughout the paper), was incorporated into poly(propylene carbonate) (PPC) by melt-blending. Characterization data by TGA and Py-GC/MS have suggested that the obtained PPC/NP-10P complex displays excellent thermal stability compared to pure PPC. The thermal decomposition temperature, with a 5% loss in weight, increases by about 103 °C from 180 °C for PPC to 283 °C for PPC with 15 wt% NP-10P. Furthermore, with only 1 wt% of NP-10P incorporated into the PPC, an increase of about 74 °C in the decomposition temperature is found. The pyrolysis mechanism of PPC before and after modification with NP-10P varies from chain unzipping degradation to chain random scission followed by unzipping degradation. The results of 31P NMR, FTIR and intrinsic viscosity measurements have illustrated that the PPC is end-capped with NP-10P, which leads to the improvement of thermal stability and the change in pyrolysis mechanism of PPC. Moreover, this new finding will facilitate development and widespread applications of this biodegradable material.

In order to improve the thermal stability of δe form of sPS that possesses nanoporous structure, benzoylation of the phenyl groups was adopted and performed by solution procedure or solid procedure. The solution procedure involves initial benzoylation of sPS in solution and then preparing δe form by solvent induction of benzoylated sPS; the solid procedure means benzoylation of δe form of sPS in solid state. Usual modifications of sPS by solution procedure greatly decrease the crystallinity of the nanoporous related δe form. In this work, sPS can well maintain its crystallinity of δe form after benzoylation by solution procedure, even when benzoylation degree reaches 20%. Thermally induced phase transition behaviors of corresponding δe form were investigated by Differential scanning calorimeter and temperature-dependent X-ray diffraction analysis. The results show that the δe–γ transition temperature increases after benzoylation by both two procedures, indicating improved thermal stability of δe form. The subsequent γ–α transition and the melting of α form both shift to lower transition temperature. Meanwhile, the transition of δe form to γ form was prohibited by solution procedure contrast to solid procedure.