This paper reports a new synthesis of biobased polymers by using itaconic anhydride (IAn) and lactic acid (LA) as renewable starting materials. Poly(lactic acid) (PLA)-graft copolymers were synthesized via two approaches. First, the macromonomer approach utilized IAn for Sn-catalyzed synthesis of PLA-containing macromonomers (IAn-PLA Macro). The macromonomer was radically copolymerized with n-butyl methacrylate (BMA), n-butyl acrylate (BA), methyl methacrylate (MMA), and ethyl methacrylate (EMA) to give efficiently graft copolymers (PLA-Graft copolymer (I)) with molecular weight M n up to 1.61 × 105 having biomass content higher than 34 wt %. Second, the copolymer approach employed first IAn as comonomer for radical copolymerization with BMA, giving rise to IAn-BMA copolymer with M n higher than 5.76 × 104. Then, Sn-catalyzed grafting of PLA onto IAn moiety of the copolymer produced PLA-Graft copolymer (II) with M n higher than 5.88 × 104, showing biomass content ≥29 wt %. In addition, radical homopolymerization of IAn was examined to give polyIAn. By using these two approaches employing IAn as a starting reactive material, PLA-graft copolymers were obtained as “biomass-plastics”. Properties of PLA-Graft copolymers (I) were also examined, which revealed possible applications for coatings and plastics. Furthermore, the IAn-containing graft copolymers will be a convenient starting biomass polymer having reactive IAn moiety in the main chain for further grafting or various functional group-introducing reactions.

For developing broader application of biobased polymers, graft copolymers and comb polymers having poly(lactic acid) (PLA) side chains have been synthesized by using a macromonomer technique. PLA macromonomers (MMm) having a methacryloyl polymerizable group with different PLA chain length with an average length m = 4, 6, 8, 12, 18, and 30 were prepared via ring-opening polymerization of l-lactide using hydroxyethyl methacrylate (HEMA) initiator catalyzed by Sn(Oct)(2). Radical polymerization behaviors of these macromonomers were examined. Radical copolymerization of MMm (m = 4, 6, and 8), with vinyl monomers like n-butyl methacrylate (BMA) and n-butyl acrylate (BA) in water as the reaction medium, gave stable miniemulsions of poly[n-butyl (meth)acrylate-graft-lactic acid]s [PB(M)A-g-PLAm]. MMm with m value higher than 12, however, gave aggregate products in a minor amount besides miniemulsions in a major amount, producing not a stable emulsion system of graft copolymers. The solution copolymerization, on the other hand, produced a wider variety of the graft copolymers, where a wider range of MMm (even m ≥ 12) can be employed. In a 1,4-dioxane solution, the radical copolymerization of MMm with BMA and methyl methacrylate (MMA) gave various graft copolymers [PB(M)MA-g-PLAm]. A new type of comb polymers (PMMm) having PLAm as pendant side chains were obtained by radical homopolymerization of MMm in a 1,4-dioxane solution. The graft copolymers and comb polymers obtained here are amorphous. Physical properties of the polymers from miniemulsions suggested them to be applicable for coatings or elastic materials which are environmentally desirable as a new class of biobased polymers. In addition, the present approach provided fundamental information on relationships between the length of PLA side chain and the bulk properties of the product polymers.

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The virus-encoded Tat protein is essential for HIV transcription in infected cells. The interaction of Tat with the cellular transcription elongation factor P-TEFb (positive transcriptional elongation factor b) containing cyclin T1 (CycT1) and cyclin-dependent kinase 9 (CDK9) is critical for its activity. In this study, we use the Fluoppi (fluorescent-based technology detecting protein-protein interaction) system, which enables the quantification of interactions between biomolecules, such as proteins, in live cells. Quantitative measurement of the molecular interactions among Tat, CycT1 and CDK9 has showed that any third molecule enhances the binding between the other two molecules. These findings suggest that each component of the Tat:P-TEFb complex stabilizes the overall complex, thereby supporting the efficient transcriptional elongation during viral RNA synthesis. These interactions may serve as appropriate targets for novel anti-HIV therapy.

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