Ultrafast 4D printing (<30 s) of responsive polymers is reported. Visible-light-triggered polymerization of commercial monomers defines digitally stress distribution in a 2D polymer film. Releasing the stress after the printing converts the structure into 3D. An additional dimension can be incorporated by choosing the printing precursors. The process overcomes the speed limiting steps of typical 3D (4D) printing.

We report an ab initio emulsion reversible addition−fragmentation chain transfer (RAFT) polymerization of styrene using poly(acrylic acid-b-styrene) trithiocarbonate as surfactant and RAFT agent. The system is characteristic of high polymerization rate, controlled polymer molecular weight, and free of coagulum. Design of the amphiphilic RAFT agent is found to be critical for the success. Poly(acrylic acid) neutralization increased the colloidal stability but led to uncontrolled molecular weight development and broad molecular weight distribution, attributed to small size and thus large number of micelles resulting in continuous particle nucleation. Polystyrene with molecular weight up to 120 kg/mol and block styrene−butylacrylate copolymer with well-controlled molecular weight were readily synthesized with this method.

The chain sequence of a poly(styrene-co-methyl acrylate) copolymer is designed to form a V-shaped gradient sequence via controlled/living radical emulsion copolymerization. This specially designed chain sequence gives this common copolymer the capacity of multishape memory. The copolymer can sequentially recover to its permanent shape from three or more previously programmed temporary shapes with the stimulus of temperature.

The Smith-Ewart equation has been modified to describe the kinetics of reversible additionfragmentation transfer (RAFT) (mini)emulsion polymerization. Two types of radicals (propagating and intermediate) are taken into account. The influence of RAFT reactions on the (mini)emulsion polymerization kinetics is investigated using the modified Smith-Ewart theory. In a simplified zero-one case, the average number of propagating radicals per particle can be described by n j RAFT -1 ) n j blank -1 + 2K[RAFT] 0 , where K is the RAFT equilibrium coefficient. It is found that the rate retardation is an intrinsic kinetic property of RAFT (mini)emulsion polymerization. The miniemulsion polymerization of styrene is also carried out with styrene oligomers of 1-phenylethylphenyl dithioacetate (PS-PEPDTA) and 2-cyranoprop-2-yl dithiobenzoate (PS-CPDB) as the RAFT agents. The experimental n j data are well described by the theory. The K values are estimated to be 314 L/mol for PS-CPDB and 22 L/mol for PS-PEPDTA. The fragmentation rate coefficients appear to be on the order of magnitude of 10 4 -10 5 s -1 .

A series of well-controlled polystyrene-b-poly(n-butyl acrylate)-b-polystyrene triblock copolymers were prepared by emulsion polymerization with a carefully designed amphiphilic macroRAFT (reversible addition-fragmentation chain transfer) agent. The triblock copolymers were produced within four hours and only a few percent of dead chains were estimated. Tensile strength of the materials was a function of composition only and it increased linearly with polystyrene composition up to 50 wt %. The ultimate tensile strength reached 10 MPa with an elongation at break of 500% at the polystyrene composition of 40-50 wt %.

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The ionic liquid 1,1,3,3-tetramethylguanidinium lactate (TMGL) was supported onto porous silica particles via a facile impregnation-vaporization method. The TMGL-supported particles gave high porosity and large specific surface area. The SO 2 sorption/desorption properties of the silica-supported TMGL (TMGL-SiO 2 ) were evaluated, and high SO 2 sorption capacity and rate were achieved. Its capacity reached 0.6 g SO 2 /g TMGL in 15-30 min with pure SO 2 gas and 0.15 g SO 2 /g TMGL in 17 h with a N 2 /SO 2 mixture gas that contained 2160 ppm SO 2 . The SO 2 concentration was reduced to 12.6 ppm after sorption. The TMGL-SiO 2 system could be reused for many sorption/desorption cycles without change in its capacity. It was also characterized by good mechanical strength and thermal stability at temperature up to 130°C. The SO 2 sorbent system appears to be useful in gas desulfurization.

It is well-known that controlled/living radical copolymerization (CLRcoP) yields gradient copolymer with the composition varying along chain length. The composition distribution of the as-synthesized product is solely determined by the comonomer reactivity ratios and is thus not well controlled. This work reports the first experimental example of the control over the copolymer composition distribution through semibatch operations. Using styrene (St)/butyl acrylate (BA) as a model system, we synthesized uniform and linear gradient copolymers via semibatch reverse addition-fragmentation chain transfer radical polymerization (RAFT) mediated by benzyl dithioisobutyrate. The comonomer feeding rate profiles for the targeted distributions were designed from a newly developed computer model that was trained from the batch RAFT copolymerizations of St and BA at different monomer compositions. The semibatch copolymerization yielded precise copolymer products having their composition distributions exactly as targeted and the polymerization rate and molecular weight profiles as predicted by the model.